It is in the Stadium Car Park, Church Road, Cheriton and opened for the first time today (Tuesday).
The site will be used by people who have coronavirus symptoms - a high temperature, a new continuous cough, or a loss or change to sense of smell or taste - and have booked an appointment through the NHS system.
It has been designed so people can walk to the site for a test, rather than arrive in a car.
It is believed services will run seven days a week, 8am to 8pm.
Those being tested will be required to follow public health measures, including social distancing, not travelling by taxi or public transport, practising good personal hygiene and wearing a face covering throughout, including while travelling to and from the testing centre.
It is being run by the Department of Health and Social Care (DHSC), although Kent County Council and Folkestone and Hythe District Council liaised with the government body prior to set up.
A letter sent to residents living near the site, from the councils, explained: "The purpose of this walk-in facility is to provide local access for testing residents who can’t or don’t drive.
"As you know, cases of coronavirus infection have begun to rise locally and nationally and Folkestone and Hythe, with the rest of Kent, has been allocated Tier 3 status as part of the government’s Covid Winter Plan.
"With limited testing facilities for those residents that cannot drive in the area, this site was chosen by Kent County Council and Public Health England (PHE) because it offers easy access and can be reached within a 30-minute walk by many residents of Folkestone.
"The test site will work in such a way as to ensure that people arriving for a test are kept separate from nearby buildings and in a way that minimises disruption to local residents.
"Those being tested will be encouraged to walk to the facility and advised not to come by car when they book an appointment.
"We understand that some local residents may be concerned that having a testing facility nearby may increase their risk of exposure to coronavirus.
"We want to take this opportunity to reassure you that there is no evidence from DHSC or PHE that residential proximity to a facility increases infection rates, and that strong safety measures will be put in place."
The letter adds security will be provided at the site.
Health Minister Lord James Bethell said: "To respond to the coronavirus, we have built a major testing and tracing system from scratch.
"We are constantly working to expand and improve it with new technologies and innovations so everyone with symptoms can get a test.
"New walk-in sites like this one makes it even easier to get a test no matter where you live.
"If you have symptoms of coronavirus, I urge you to book a test today and follow the advice of NHS Test and Trace if you are contacted to protect others and stop the spread of the virus."
The testing centre is being operated in partnership with Mitie and will offer self-administered tests.
In the last seven days, 466 people in the district tested positive for Covid-19.
The case rate stands at 412 cases per 100,000 people, and Folkestone and Hythe is now listed among the top 20 places in England with the worse infection rates.
It comes as asymptomatic testing sites for Covid-19 have been announced for Swale and Thanet this week, in another bid to tackle the county's rampant rates of coronavirus.
Swab tests will be offered to those who do not display symptoms of the virus but may be unwittingly spreading the illness.
This week will also see an extension of the vaccine roll out, with GPs now able to give the jab as well as staff in hospitals.
The William Harvey is still the closest location to Folkestone district to be providing the vaccine to those over 80.
Last week, Romney Marsh resident Kenneth Lamb was the first person in Kent to receive the jab.
To book a test visit nhs.uk/coronavirus or call 119.