Considering the evidence of the influence of humidity on the performance of a coal-fired power plant, thisresearch aims to answer the following questions: Which parameters of the drying process of the coal in a vertical millhave more importance to the superheated steam generator (SSG) efficiency? Does humidity (fuel and air) affect theSSG efficiency of a coal-fired power plant? To answer these questions, the Response Surface Methodology (RSM) isused to analyze and optimize the coal pulverizing system and the experimental design method used is Box-Behnken. Theexperiments will be performed on a model developed in the EbsilonR©Professional software. The first RSM results showedthat the most important parameters for the lower moisture content coal are P2, P3, and P5; for the medium moisturecontent coal are P2 and P5; and for the high moisture content coal are P2 and the interactions of P3P2 and P3P4.Then, the second RSM results showed the efficiency decreases with the increase of the humidity in the coal, but it did notchange with the humidity of the air.