The technology of measuring vital signs by millimeter wave radar has great medical value. However, as a kind of noise signal, respiratory harmonics and human random movement signal seriously affect the extraction of heart rate. In order to solve the above problems, this paper proposes a method of measuring dynamic target heart rate based on multi-detection signal separation technology and adaptive noise cancellation algorithm according to the characteristics of different breathing modes. The method comprises the following steps of: simultaneously measuring chest and abdominal micro-motion signals of a person to be measured by using a 77 GHz frequency modulation millimeter wave radar; separating the chest and abdominal baseband signals by using a newly proposed multi-detection point signal separation technology based on the chest and the abdomen; eliminating noise signals by using an adaptive noise cancellation algorithm; and performing frequency spectrum analysis on heartbeat signals to obtain a heartbeat frequency. Experiments show that the method can effectively eliminate the noise signal interference in the state of human random movement, and the error rate of heart rate measurement is only 1.19% in multiple measurement experiments of a single target, which is 0.97% lower than that of multi-channel Kalman smoother method.