Abstract: Analyzing error characters of inertial sensors and modeling errors are important tasks when building Inertial Navigation Systems (INS) and effective ways to improve accuracy of INS. Non-stochastic error characters and error sources of a typical kind of MEMS gyroscope in structures and Comb-drive Tuning Fork Gyroscope (TFG) are researched. The effects of interfering torques are discussed from the aspect of two-order weakly damped control systems. The open-loop sensitivity of the gyroscope is focused on and its variation versus temperature, specific force and angle rate is brought forward to under some simplified conditions. Finally, the form of the non-stochastic error model is concluded and the conclusion is much helpful and instructional to modeling non-stochastic errors of TFG.