The cracks were pre-settled to the R.C. frame structure caused by earthquake which was defined as the damage index ω during the modeling process with analysis software-ANASYS. The temperature field contour curve were calculated for the column and beam, the law of deteriorated bearing capacity with time for the R.C. frame structure under elevated temperature were brought forward，which can adapt to R.C. frame structure with different damage index ω caused by earthquake.The relationship between ω and deteriorated bearing capacity for R.C. frame structure was also given, which was proved to be effective and correct according to comparison with the data recorded from the elevated temperature experiment designed by author.