For solving the data deviation problem in solution thermodynamics high temperature test, analyze activity of binary alloy of f Cu-Pb and Cu-Sn. According to basic characteristics melt element, establish the activity calculation model, analyze influence of temperature and binary alloy element on activity, use Miedema model to predict the activity and activity coefficient of binary alloy, acquire activity and activity coefficient by calculation, and compare with test data. The test results show that the calculation result is fit for test result.