Abstract: Analyzed in the essay is the yield strength variation regularity of the14.10 mm X70 steel plate before and after the pipe-forming process.Based on the analysis, and the test result and the statistic data of the properties as obtained from the massive production two methods respectively using the yield strength as R_t0.5of the steel plate, and the tensile curve morphology(i.e., the metallographic structure type)of the steel plate are established to predict the yield variation regularity of the steel plate before and after the pipe-forming process.The analysis leads to such as conclusion that the higher the 14.10 mm linepipe-purposed X70M steel plate is, the lower this value will be after the pipe-forming process, and vice versa.