Abstract: According to GB/T 7314-2005 Metallic Materials-Compression Testing at Ambient Temperature, The mathematical model for evaluating the measurement uncertainty of compressive strength of metallic plastic materials was established. And with Q235 steel as an example, the uncertainty components caused by sample cross-sectional area calculating and universal testing machine force measuring were evaluated, respectively. The results show that the compressive strength of the test Q235 steel Rmc=(645±5) MPa when the coverage factor k=2.