The main error factors affecting the accuracy of interferometric fiber optic gyroscopes (I-FOGs) were firstly analyzed. Subsequently, the influence of test equipment, such as angular rate turntable, test fixture and time reference source, on the error of I-FOGs were researched. Finally, a suppression method based on the high-precision counter for the accuracy evaluation of the turntable combined with the long-period and fixed-cycle test method of the turntable was proposed.With this method, the experimental results demonstrate that the zero bias test error caused by the test fixture error is reduced by 66.7%, both the scale factor absolute error caused by angular rate turntable error and the scale factor repeatability error caused by time reference error are reduced by an order of magnitude. This research is of great significance to the experimental equipment improvement and accuracy improvement of I-FOGs.