To systematically solve the application problems of Measurement System Analysis (MSA) in the automatic hardness detection system, the particularity of its MSA is expounded, and points out the limitations of the traditional Gauge Repeatability and Reproducibility (GRR) method in the identification of variation sources and experimental design. On this basis, a "process decoupling hybrid GRR" experimental strategy is proposed, which decouples the hardness testing process into two sub processes: indentation generation (destructive) and indentation measurement (non-destructive). Nested design and cross design are used to separate and quantify the variation sources, respectively. Through the construction of an automation platform with double detection units, the systematic MSA experiment was conducted, and the analysis of variance was used to evaluate the influence of equipment repeatability, reproducibility and interaction. The results show that the proposed method can effectively identify the dominant variation sources, and provide a feasible analysis framework for the performance evaluation and optimization of the automatic hardness testing system, which has strong engineering applicability and popularization value.