In stabilization systems disturbed by base motion, attitude estimation process is very important, because stabilization performance depends on disturbance rejection capability based on attitude estimation. For the accurate stabilization, at least 3 states representing system's motion are required to be measured or estimated, and transforming these states to global coordinates should be accompanied in general. However in most practical cases of stabilization system mounted on a mobile vehicle, only 2-axes gyro sensor is used to sense the pitch and yaw angular rates of the system excited by vehicle motion. In this study, we analytically derived stabilization errors to be generated in system with 2-axes gyro sensor with some reasonable assumptions, and verified them through simulation studies with various vehicle motions in typical traveling conditions. Simulation results and analytic error formulas show that stabilization performances are almost same regardless of coordinates-transformation process, and biased roll angle dominantly induces accumulation of errors when 2-axes gyro sensor is used for stabilization system.