Based on the calculation methods of nominal water-cement ratio of mortar and average paste thickness of standard sand provided by authors, the nonlinear relation between fluidity of mortar and nominal water-cement ratio of mortar, average paste thickness of standard sand, fly ash-binder ratio was established by using artificial neural network(ANN). The outcome of this paper can be used in determining the effect of water reducer, and lays the foundation for the prediction of concrete slump and the mix proportion design of higher volume-stability concrete.