System and method for shear wave elasticity imaging performa) acquiring B-mode ultrasound images of a target region；b) selecting a region of interest；c) transmitting a shear wave excitation pulse；d) measuring displacements of tracking focal points or depth ranges at different depths positions along each of laterally staggered tracking lines within the selected region of interest；e) determining a curve representing displacement of tissue as a function of time at different spatial locations within the region of interest；f) determining for spatial locations candidate time(s) of arrival of the shear wave at the spatial location as a function of the curve；g) finding linear functional relation between the time of arrival and the spatial coordinate in the lateral direction using Random Sample Consensus (RANSAC) algorithm； andh) determining the inverse of velocity of the shear wave in a spatial location as the angular coefficient of the linear function.
