Aiming at the problem of low accuracy in non-contact measurement of respiratory rate (HR) and heart rate (BR) in indoor complex environment, this paper proposes a vital sign detection method based on 77GHz mmwave radar perception. Through multiple experiments at different distances from the radar and taking the measured data of Mindray ECG monitor as a reference, the accuracy of this method is verified. Firstly, the multi pulse if signal is processed by incoherent accumulation technology between pulses to improve the signal-to-noise ratio (SNR) and signal amplitude. Then, the target detection method based on distance dimension FFT spectrum and CA-CFAR adaptive threshold is used to extract the human target phase information from the indoor complex environment, and the respiratory and heartbeat signals are separated by FIR band-pass filter. The improved smoothing filter combined with the second-order phase difference method is used to remove the noise and reduce the impact of respiratory harmonics on the heartbeat signal. Then, the root MUSIC algorithm is used to obtain HR and Br. Finally, the measurement results of Mindray ECG monitor are used as a reference to verify the measurement accuracy of this method. The experimental results show that the average absolute error rates of HR and Br obtained by this method are less than 5.08% and 2.61% respectively, and the average absolute error is 0.94bpm and 1.97bpm. Therefore, this method can improve the measurement accuracy.