The invention discloses a high-resolution strain testing method.According to the method, two parts which are different in rigidity ratio and length ratio are adopted for a connection combination with a certain structure, deformation with an effective distance is concentrated on one part by means of a mechanics principle, and the effect of mechanically amplifying bridge strain is achieved.Accordingly, a corresponding testing device is further designed and made by the inventor.By means of the testing method and the testing device, high testing accuracy is achieved by combining a high-accuracy strain solving formula which is derived by the inventor through material mechanics and structural mechanics methods on the basis of part parameters of the rigidity ratio and length ratio, the testing accuracy reaches 0.01 microepsilon or above, and the high-resolution strain testing method and testing device can be widely applicable to the technical fields of bridge load tests, health monitoring and moving load identification based on dynamic strain and the like.