Pole assignment method is one of the algorithms for calculating the control force in active control of structures. One of the problems of control systems is time delay due to data processing and apply control force to structure that will reduce the efficiency of the control algorithm. In this study, the effects of time delay on pole assignment method for the control of structures, as well as how to reduce its effectiveness will be evaluated. In order to reduce or remove the effect of time delay, delay term will be considered in the original equation in the beginning of the affair. It is carried out by using the Taylor series, and importing the time delay term in the matrixes of the system. Thus, the equations of the structure are simplified and will be solved such as simple equations without time delay. The obtained equations are studied by using pole assignment method and the optimal control force is calculated.