As increasing demands for high-speed InGaAs photodetector in space application, it is more significant to research the effect of space radiation on high-speed InGaAs photodetector. Using the real-time measurement, the variation in the responsivity, 3dB bandwidth, dark current of high-speed InGaAs photodetector irradiated with different γ radiation dose and rate was studied. By anaylzing the real-time measurement data, it shows that the dark current rise with the increasing of radiation dose or rate, but the responsivity and saturation optical power slightly change under different γ radiation dose and rate. The results indicate that γ radiation has less effect on high-speed InGaAs photodetector.