To explore the characteristics and development law of sand liquefaction in Tai'an County, Liaoning Province, a series of undrained dynamic triaxial tests were carried out to study the variation of dynamic pore pressure and dynamic strain of Tai'an sand under dynamic load. The main factors affecting the sand liquefaction were analyzed, and the dynamic response characteristics of sandy soil under dynamic loads were revealed. The results showed that the ud curves of samples with different dynamic stress include two types: steep increase in the late stage and uniform increase. When the dynamic stress amplitude is large, the u_d increases at a fast rate, showing the characteristics of uniform increase; when the dynamic stress amplitude is small, the u_d curve slowly increases in the initial stage and steep increases in the later stage. Relative density Dr and dynamic stress amplitude CSR are the main factors that determine the liquefaction of sand soil. Under the equivalent dynamic load, the CSR gradually accelerates with the continuous development of Dr. When the Dr is large enough, the sand soil is basically in a dense state and liquefaction is difficult to occur. Under the action of cyclic load, the dynamic response of Tai'an sand include three stages, i.e., overall compression, tension-pressure balance and tension in the initial, middle and later stages, respectively. At the later stage, the tensile strain of the specimen increases rapidly, which is prone to tension failure. The research results provide a theoretical support for the seismic design of buildings in Tai'an area, Liaoning Province.