This paper takes a triple distillation column as the object and introduces the design of neural network control system(NNCS) in distillation process.The NNCS introduces NN preestimater and NN controller.The NN preestimater is used to express the nonlinear relation between the input and the output.The NN controller is used to realize the decouple control on NN preestimater.BP network is used and realized on a parallel system of 9 Transputers.