Abstract: The laser interferometric measurement system for space gravitational wave detection is of great significance for detection tasks, the noise of the interferometric measurement system is the key factor determining the success or failure of the task. Laser frequency noise is one of the most important noises. Therefore, it is necessary to analyze the impact and importance of laser frequency fluctuations on measurement results. Due to the difficulty in simulating the environment in space, analyzing based on simulation systems is an ideal approach. Based on the simulation system of space gravitational wave detection laser interferometry measurement, the measurement errors caused by laser frequency fluctuations of free running laser on the measurement results of scientific interferometer, reference interferometer, and TM interferometer models was analyzed. Then, sensitivity analysis was conducted using the derivative method and Sobol method with interference laser wavelength as input parameter. The influence and importance of laser frequency fluctuations of reference beam and measurement beam on the output of three interferometer models were analyzed. The results indicate that: laser frequency fluctuations during free running stages, which will cause changes in the measurement results of the interferometer, these changes are far greater than the picometers. Additionally, under the experimental conditions of this paper, the importance of measurement beam frequency fluctuation on the outputs of the three interferometers is 100%, 56%, and 54% respectively. The importance of reference beam frequency fluctuation on the outputs of the three interferometers is 0%, 44%, and 46% respectively.