Abstract: The creep curves of heat resistant steel 12Cr1MoV was inveshgated. By constant stress creep tests. The creep curves of consent stress creep are quite different from that of constant load creep. The original θ-Concept Project procedure can be validared to successfully describe the constant stress creep curves but not constant load creep. A modified θ procedure was developed. This approach can successfully described both constant stress creep and constant load creep curves. The new approach leads to a great improvement in accuracy of long term prediction of extrapolation due to validation of a great number of existing constant load creep data.