It is found that optimal backcalculation point may be exist during the modulus backcalculation in the three layers structure of asphalt pavement. Through a large number of modulus backcalculation confirmed the existence of the optimal balckcalculation point and found the position of the optimal backcalculation point, try to explain the inevitability of existence of the optimal backcalculation point in theoretically. The writer compares the backcalculation method with domestic and foreign modulus backcalculation method through precision and efficiency, it is confirmed that the backcalculation method using optimal backcalculation point, precision and efficiency of this method are all very high which make the possible of massive modulus backcalculation.