Traditional strapdown inertial navigation system(SINS)algorithm studies are based on ideal measurements from gyros and accelerometers, while in the actual strapdown inertial measurement unit(SIMU), time-asynchrony between each inertial sensor is inevitable. Testing principles and methods for timeasynchrony parameter identification are studied. Under the singleaxis swaying environment, the relationships between the SINS platform drift rate and the gyro time-asynchrony are derived using the SINS attitude error equation. It is found that the gyro timeasynchrony error can be considered as a kind of pseudo-coning motion error caused by data processing. After gyro testing and synchronization, the single-axis tumble test method is introduced for the testing of each accelerometer time-asynchrony with respect to the ideal gyro triad. Accelerometer time-asynchrony parameter identification models are established using SINS specific force equation. Finally, all of the relative time-asynchrony parameters between inertial sensors are well identified by using fiber optic gyro SIMU as experimental verification. Traditional strapdown inertial navigation system (SINS) algorithm studies are based on ideal measurements from gyros and accelerometers, while in the actual strapdown inertial measurement unit (SIMU), time-asynchrony between each inertial sensor is inevitable. Testing principles and methods for time asynchrony parameter identification are studied. Under the singleaxis swaying environment, the relationships between the SINS platform drift rate and the gyro time-asynchrony are derived using the SINS attitude error equation. It is found that the gyro time asynchrony error can be considered as a kind of pseudo-coning motion gyration caused by data processing. After gyro testing and synchronization, the single-axis tumble test method is introduced for the testing of each accelerometer time-asynchrony with respect to the ideal gyro triad. Accelerometer time-asynchrony parameter identification models are established using SINS specific force equation. Finally, all of the relative time-asynchrony para meters between inertial sensors are well identified by using fiber optic gyro SIMU as experimental verification.