Abstract: A computational model for triangular plate element under arbitrary excitation is established and a refined dynamic formulation taking in account the local effect is presented. With the present model, refined dynamic analysis of structures with complex boundaries can be performed. A cantilever plate is studied by conducting time-history analysis and modifying its local effect. The results are compared with those obtained using quadrangle plate element. It is shown that the local dynamic effect is directly proportional to the acceleration and the neglect of local effect results in significant differences of dynamic internal forces with their theorectical values. Thus, the local dynamic effect must be considered in the dynamic formulation for triangular plate element.