Aimed at the problems that evaluation of pavement damage area in current standards is not clear enough, a current asphalt pavement condition evaluation model is introduced. If the repair area width reaches the pavement width, this should not be involved in pavement damage condition evaluation. Conversion coefficient K of repairing damage area should be 0.7. A Matlab testing method based on Mandonte Carlo algorithm is put forward to examine the rationality of K being 0.7. The concrete conditions are as follows: First, input the known data to Matlab to fit, and then, derive the functions of elements obey affected pavement condition index, such as repair area, total crack length and other damage areas, etc., Last, calculate the corresponding PCI to get the result of pavement condition evaluation by using Monte Carlo algorithm. Through the comparison with the actual pavement conditions and the actual test, the rationality of K being 0.7 is verified.