The invention discloses a material fatigue strength testing device and a testing method. The device comprises a nozzle (2) arranged on the sidewall of a cuboid testing slot (1). A rectangular spout (3) is arranged in the nozzle (2). The bottom of the cuboid testing slot (1) is also provided with a drive screw (4) and a slide rail (9). The drive screw (4) and the slide rail (9) are used for making a reed which is prepared from a material to be measured and is installed on a base or vice (8) to directly face the spout (3). The device of the invention can rapidly determine material fatigue strength, has fast testing speed, has a simple structure and is low-cost.