In many application fields of narrow linewidth lasers, laser frequency stability is an extremely important parameter, and characterizes the degree of frequency stability. Based on the virtual difference between passive frequency stabilization and active frequency stabilization——having stable frequency reference standards or not, laser frequency stabilization techniques are studied, especially for active frequency stabilization: classification is done based on the selection of frequency standards; the theory and reason of reaching different precisions of frequency stabilization technologies commonly used are analyzed; advantages and disadvantages are compared based on reports of the active frequency stabilization at home and abroad. By comparison repeatedly, the PDH technology has obvious advantages, can obtain high frequency stability.