Alison Clarke's pay rose from £98,000 a year when she took up the post in 2006 to £157,000 at the end of 2012 – £15,000 more than Prime Minister David Cameron earns.
But, according to education watchdog Ofsted's latest report, the leadership and management of the college have worsened since she started.
Canterbury College principal Alison Clarke
A 2007 Ofsted report ranked leadership and management as "good: grade 2", while the report following the inspection in November rated it as "requires improvement: 3”.
When Ms Clarke became principal in early 2006, she said: "I want us to be among the best in the country."
However, Ofsted's latest report rates it as "3 requires improvement" and states: "Too much teaching and learning require improvement and the proportion of good and better lessons is low.
"Leadership and management have not yet secured consistently good quality teaching and learning for all learners at all levels."
Canterbury College in New Dover Road, Canterbury
It also says there are weaknesses in the teaching of English and maths.
Ofsted's inspectors list the college's strengths as helping students get jobs and good teaching in subjects such as health, early years, science, business and accounting, finance, teaching and lecturing and as having "very good arrangements for safeguarding learners".
Ofsted rates institutions from "1 outstanding" to "4 inadequate".
The college, in New Dover Road, which has 5,100 full-time and 1,100 part-time students, is defending the pay increases for Ms Clarke because of her successful financial management.
Ofsted said Canterbury College's leadership and management has worsened
Spokesman Chris Thomas said: "When Alison Clarke became principal the college was in the lowest 3% of the sector for student funding rates.
"Since then the college's income has grown 46% and the college has generated healthy surpluses which have enabled it to reinvest in IT and other key resources for learners, staff, business and the community.
Canterbury City Council chief executive Colin Carmichael is the chairman of the college's corporation, effectively its board of governors.
"The college is now in the top 5% of the sector financially, having just been judged as outstanding for its financial management by the Skills Funding Agency."
He added: "Public sector salaries are always in the spotlight, not least during tough economic times.
"We are very confident that the principal has provided consistently good value having taken the college to the financially secure point it is today."