The invention discloses an overwater building construction platform and an erecting method thereof, as well as a method that uses the construction platform to conduct overwater building construction. The overwater building construction platform comprises a base, a longitudinal beam, a cross beam, a walkway board and a protective barrier. The erecting method of the overwater building construction platform comprises the steps of: steel pipe pile inserting and piling, cross bridging welding, longitudinal beam installing, cross beam installing, walkway board installing, and protective barrier installing. The method using the construction platform to conduct overwater building construction comprises the steps of: construction platform erecting, building pile foundation construction, building beam column construction, construction platform dismantling, and building floor slab construction. For the overwater buildings such as an overwater restaurant, a scenic pavilion and an overwater dock of which the structure bottom elevation above the pipe is higher than the water level elevation, which are located in inland rivers or lakes, the overwater building construction platform and erecting method and use method thereof adopt the cofferdam-free construction scheme, can effectively solve the disadvantages of cofferdam construction, reduces the construction costs, and shortens the construction period.