The invention relates to a waterproof circular electric connector, which comprises a plug and a socket, wherein the plug consists of a clamping cap, a head shell and a jack which is connected with a sealed sealer; the socket consists of a square seat and an inserting pin which is connected with a sealed sealer; a seal ring is arranged on an inserting end face of the plug and the socket and arranged inside the plug and inside a sealing groove on a front end face of a supporting panel of the head shell; and both the inner wall of the head shell of the plug and the inner wall of the square seat of the socket are provided with sealing grooves which are matched with the circumferences of the sealed sealer. The electric connector is convenient to plug a head seat, has long service life and goodsealing performance and water resistance, and is suitable to be used in various deep-water hermetic situations.