Abstract: To solve the problem that the Doppler method cannot detect the cycle slips due to the low observation accuracy of the single-frequency GNSS receivers on high earth orbit（HEO）satellites，a cycle slip detection method based on the Kalman filter smoothed Doppler observations was proposed.Firstly，the Doppler observations were smoothed by Kalman filtering to reduce the influence of noise.Then，the smoothed Doppler observations and carrier phase observations were adopted by Doppler method to calculate the cycle-slip detection value which should be differenced between epochs to improve the cycle-slip detection rate.The GNSS observations data received by CE-5T1 mission return vehiclse were used.The proposed method can detect the cycle slips more accurately than the traditional Doppler method in a low signaltonoise environment，which can support the future GNSS experiments on HEO satellites.

Key words: GNSS, HEO, single frequency cycle slip detection, Doppler observation, Kalman filter