Abstract: The general expression of the spatial cross-spectral density function of the ambient sea noise field is developed, which is based on the theory of "local spectrum of underwater ambient noise field" presented by Xu Zhen-yong (1977). Spatial Cross-spectra of several typical cases are calculated. The resultant expression for deep-sea model with the uniform sound velocity profile is identical with that by Cron and Shermen (1962, 1965) except an additional term which is due to inhomogeneous plane waves and can be neglected when the depth of receivers is much greater than the separated space distance. Finally, the comparison of some theoretical calculations and previously obtained experimental data is also given.