Thermal power generation process undertakes the important task of power supply. Grasping the operating performance of thermal power generation process has great significance for improving the utilization rate of coal resources and the comprehensive economic benefits. A new assessment method based on hierarchical multiblock performance-relevant independent component analysis(HMPRICA) is proposed in this study. The whole process is divided into multilayer and multiblock in the horizontal and vertical directions. The assessment models based on HMPRICA can not only effectively extract the variation information closely related to the process operating performance, but also extract the influence of the interaction among different subsystems. The proposed method can reduce the complexity of each assessment model and improve the interpretability of the assessment results. When the process is nonoptimal, the responsible causes can be accurately located according to the subsystem assessment results and variable contribution rate. Finally, an actual thermal power generation process is taken as the background to verify the effectiveness of the proposed method.