To measure the level attitude of moving carriers (such as vehicles, ships, aircraft, etc.) in real-time and highly precisely, based on liquid′s automatic level, a method combining high-precision optical angle measurement, inertial synchronous multiplexing platform and level error detection tool is proposed and tested on a docking ship. The test result confirms the correctness, effectiveness and feasibility of this method. The difference D-value between the level attitude measurements of test equipment and inertial equipment is not larger than 2.0″ [root mean square (RMS)]. This method can be used in high-precision measurement of level attitude, measurement of structural deformation and accuracy evaluation of inertial system of moving carriers such as different kinds of military weapon launching platforms.