Based on fiber optic gyroscope technique new method of rotation angle testing in three-axis vibration is proposed in this paper, and the theory of fiber optic gyroscope is introduced as well. According to the measurement accuracy requirement, the angle testing system of FOG is designed by analyzing the environment of three-axis vibration. It was applied in experimental investigation of rotation angle in three-axis vibration with the FOG testing system and the real-time angular rate signal was processed by frequency analysis. The results of practical application show that it is feasibility and validity of angle testing method by means of FOG technique.