The founding principal of two Christian colleges is facing historical child sex abuse allegations that date back to his time at the schools, in the 1970s and '80s.

Peter Harris, who has been living in Thailand and had worked on making schools in the country sustainable under a federal government grant, was arrested at Melbourne Airport on Tuesday.

Dr Peter Harris, 78, was arrested on Tuesday night at Melbourne Airport. Credit:Support Phuket

The 78-year-old ex-principal was attempting to board a flight when he was arrested, a police spokeswoman confirmed.

Dr Harris faces five charges, including assaults in East Melbourne, Maryborough and Castlemaine between 1975 and 1983.