Due to such advantages as high parameters, big capacity, high efficiency and low coal con- sumption rate, supercritical units have got a wide-ranging use and become the backbone of the electric power grids nowadays. To give a full play of its ability to regulate the primary frequency is of a major sig- nificance to maintaining the stability of the frequency of power grids. As a result, the strategies for control- ling the primary frequency modulation of supercritical units were investigated and a model for simulating a 630 MW supercritical unit and its control system was established. The improved bilinear transformation least square identification method was used to conduct an identification of the unknown parameters in the model. On a PSD-BPA simulation platform, a model for its control system was set up. Through a simulation analysis and a contrast with the on-the-spot test data, it has been verified that the model in question is sound and correct and the relative error at the maximal power is 0.5%. The influence of the frequency modulation dead zone and the droop of the speed regulation on the ability to regulate the primary frequen- currently giving consideration to requirements for various performance indexes and making the ability of the unit to regulate the primary frequency to reach its optimum.