Abstract: According to the ultrasonic echo signal mechanism from the human blood,the distributed model firstly men-tioned in this paper represents the echo array more accurately than the conventional point source model.As a time-delay problem,a vector corresponding to a known distribution function is defined,which has two unknown parameters including a central velocity and a distribution parameter.By the two-dimensional joint search,the two parameters can be estimated using orthogonal property between noise subspace of the correlation matrix of the echo array and the time-delay vector.Then the velocity estimation is obtained from the central velocity and its validity is denoted by the distribution parameter which denotes the velocity extension.After rejecting the invalid data,the final velocity profile can be acquired.Simulation results show the good accuracy,stability and achieving the good purpose by small sampling data.