The invention relates to a low velocity free jet device with the aspect ratio of 180:1 for a light weapon test. The low velocity free jet device with the aspect ratio of 180:1 for the light weapon test comprises a steel frame, a hanging beam, a measurement and control system and 68 device bodies. The wind speed of 68 independent axial flow fans is set by the measurement and control system, and air flow pressurized in an accelerating manner enters into a diffusing section. Air flow in the diffusing section enters into a downstream equal straight section, and a damping net in the equal straight section rectifying the air flow enters into a contraction section. The airflow velocity in the contraction section increases and the air flow is discharged into a test cabinet body after the uniform degree further increases at a certain velocity. A free jet area is formed in the test cabinet body. According to the device, the dimension ratio of a crosswind area is 180:1, the wind velocity can be continuously adjusted within a range of 3-10m/s, and a test platform for the light weapon test is provided.