The invention discloses a method for detecting a bridge impact coefficient based on a dynamic load test. The method comprises the steps of: (1) detecting and recording deflection data of a bridge; (2) drawing a deflection schedule curve of the bridge; (3) obtaining a bridge impact coefficient muij corresponding to each pair of adjacent wave peak value Xij and wave trough value Yij on the i-th deflection schedule curve of the bridge; (4) obtaining a bridge impact coefficient mui corresponding to a vehicle speed vi; (5) repeating the step (3) and the step (4) until n bridge impact coefficients mu1, mu2, ...mun corresponding to n different vehicle speeds v1, v2, ...vn are obtained; and (6) obtaining a bridge impact coefficient mu. The method for detecting the bridge impact coefficient based on the dynamic load test, disclosed by the invention, has the advantages of rational design and convenience in realization; the bridge impact coefficient obtained by detection is safer, so that dynamic effect of the bridge structure can be reflected more exactly and more rationally under the function of the load of movable vehicles; the practical problem that the conventional impact coefficient cannot reflect exactly that the movable load acts on the bridge structure in form of multiple load points is solved efficiently; and the method for detecting the bridge impact coefficient based on the dynamic load test, has strong practicability and high popularization and application values.