Abstract: Gravitational wave detection imposes high stability requirements on telescopes in space. To achieve independent measurement and calibration of the optical path stability accuracy of the telescope, the research was conducted on corresponding measurement methods. Based on the principle of heterodyne interferometric measurement, a high common-mode suppression interferometric measurement scheme was designed, and an optical path noise theoretical model was established. According to the requirement of 1 pm/Hz^1/2@1 mHz for optical path stability indicators, the optical path noise level of the measurement system components was allocated. To verify the feasibility of the scheme and the accuracy of the noise theoretical model, an interferometric measurement system was constructed at the front end of the telescope. According to the relevant parameters of the experimental instruments and optical components, the theoretical evaluation of the system's optical path noise level was 7.319 nm/Hz^1/2@10 mHz. The experimental measurement result of 3 nm/Hz^1/2@10 mHz was consistent with the theoretical evaluation, indicating that the interferometric path has good noise common-mode suppression characteristics, and verifying the accuracy of the noise theoretical model. When the testing environment and instrument accuracy meet the requirements for optical path noise allocation, this measurement scheme is expected to achieve the measurement of the optical path stability of gravitational wave telescope.