We introduce a novel neural operator based on Neumann series to approximate the map from inhomogeneous coefficients to solutions in Helmholtz equation. In the architecture of the neural network, we combine the idea Neumann series, FNO and U-net such that our network is capable to capture high frequency and multiscale feature. NSNO achieves higher accuracy than FNO in the tests of Helmholtz equation and also gives good reconstruction in inverse scattering problem.