The marine environmental conditions of typhoon affected area in South China Sea (SCS) in China are complicated. The parameters of wind, wave and current speed of different return period are the basis of the selection of oilfield project and the important role of development cost evaluation. Based on the deduction method of API specification, the design criteria of the typhoon in SCS oil and gas regions with the two-layer nested model combined with typhoon numerical model is proposed in this paper. The statistical analysis of typhoon characteristics were presented, then wind speed of all the blocks in north part of SCS induced by typhoon with long return period was calculated. The prediction accuracy of the design parameters of long return period is improved by this model.