There is an abundance of motion information in micro-Doppler spectrum of walking human such as bulk velocity, gait cycle and cycle length. Furthermore, the physical parameters of walking human can be estimated using motion parameters. Motion parameter and physical parameter are both important for precise radar recognition of walking human. However, parameter estimation is very difficult because of the complexity of radar echo from walking human. In this paper, a parameter estimation method of walking human based on micro-Doppler spectrum is proposed to estimate the bulk velocity, gait cycle, cycle length, leg length and height, respectively. Reassigned spectrum is used and the torso component is separated from the spectrum first in this method. Then the five parameters are estimated using the separated torso component. The performance of the proposed method is verified with simulations finally.