The invention discloses a counterforce beam loading device for a static load test of a bridge beam body. The counterforce beam loading device comprises a counterforce loading beam which is arranged right below a test beam and a loading mechanism which is installed on the test beam, wherein the counterforce loading beam and the test beam are symmetrically arranged in the vertical direction, and a beam-end supporting cushion block is arranged between the counterforce loading beam and the test beam in a lining manner; the loading mechanism comprises an upper crossbeam, a lower crossbeam, a pressurizing mechanism, an upper ejector plate and a lower liner plate, and the upper ejector plate and the lower liner plate are connected with each other through a drawing bar. The loading device adopts a beam body which is the same as the test beam as the counterforce loading beam and has advantages of simple structure, low cost, good loading effect, simplicity in loading position adjustment, safety in loading and the like. Meanwhile, the invention also discloses a counterforce beam loading method. The method comprises the following steps of I, leveling a test field; II, hoisting the counterforce loading beam in place; III, arranging the beam-end supporting cushion block; IV, hoisting the test beam in place; V, installing the loading mechanism; and VI, loading. The method is simple in step, convenient to realize, low in investment cost, short in loading time, good in loading effect and wide in application range.