Currently, there is no way to measure the level zero value of INS (Inertial Navigation System) quantitatively when TT & C (Tracking, Telemetering and Controlling) ship is in the dynamic condition. So, there is no way to correct the new drift zero value after the ship has been launched from a shipyard. To resolve the problem, a method that using the electronic level meter to measure the level zero value of INS when TT&C ship is in the moored condition is proposed. Through the transformation of the existing electronic level meter and build a simulation system for simulating the swaying motion of a moored moored ship, the electronic level meter has the ability of dynamic measurement and study the distribution law of the dynamic measurement error in this state. Based on the law of error distribution, the level zero value measurement method of INS has been studied. Through the relevant experiments and derivation, the level zero value measurement method of INS is successfully obtained.