Synchronization is a crucial mechanism for information communication in neural network. However, how external electrical fields modulate synchronization is remain an open question. In this paper the stability of complete synchronization of coupled homogenous neural network in external electrical stimulation is investigated based on eigenvalue analysis. Furthermore, the effects of network heterogeneity and field frequency on synchronization of heterogenous neural networks are studied in detail. It's shown that coupling strength and topological structure play a crucial role in modulating the synchronous states in neural system. Synchronization is sensitive to electrical field frequency. However, heterogeneity plays an adverse role in achieving synchronous states.