Curve fitting for the calculation of ship displacement and windage area under 75% guarantee rate in the 2010 Code on Load for Harbour Engineering is carried out. The results are consistent with the norms calculation, indicating that the proposed curve fitting is applicable for the calculation of ship displacement and windage area for different types of ships. This article provides a more reasonable, simple and accurate calculation method on ship displacement and windage area for the type of ship not included in the new code on load.