This paper presents a new kind of macromodel of OTA,which can be used to solve the problem in which the two port macromodel couldnt reflect some functions of the OTA.The new model also opens up a new way for the simulation of the OTA circuit.This paper discusses the way of designing this model and simulating it in SPICE.The result proves its reasonable design and its simplicity in structure.In the application of this model,we design a complete symmetric double differential quarter square OTA multiplying unit by using four three port OTA macromodels.It successfully solved the problem of the unsymmetry of two input ports in an OTA multiplying unit.This result fully agrees with the experiment.