A three-axis angle measurement method is proposed using an optical wedge as a reflector. In this paper, the mathematical model of three-axis angle solving corresponding to the method is derived, and it is verified and corrected by establishing an optical simulation model, and, finally, the feasibility and measurement accuracy of the method are verified by using a principle prototype. The experimental results show that the RMS values of the measurement errors of pitch angle α, yaw angle β, and roll angle γ are 6.27 ' ' , 4.35 ' ' , and 17.68 ' ' , respectively, within the measurement range of ±2∘, and the measurement accuracy is insensitive to the measurement distance.