The invention discloses a connection device for a horizontal actuator and a reaction wall and relates to the technical field of a quasi-static test device. The connection device comprises the reactionwall. The reaction wall is equipped with an adjusting mechanism and a connecting mechanism. The adjusting mechanism comprises a support bottom plate a, a support supporting plate, a connecting plateand a stay cable. The connecting mechanism comprises a support bottom plate b, a cross rib plate, a top plate, a connector and an actuator loading piston. The adjusting mechanism and the connecting mechanism are connected in a welding manner; the device is light in weight, convenient to mount or dismount and convenient to move; the device is simple to process and manufacture and low in productioncost; the connection device has the adjusting mechanism, and by adjusting a fastening mechanism, levelness of the horizontal actuator can be adjusted accurately; and through elliptical long bolt holes, the horizontal actuator can be finely adjusted in a horizontal plane, so that the horizontal actuator can be accurately connected with a test piece.