The invention relates to a mini pile horizontal static load test device and method. The device comprises a datum beam, magnetic gauge stands, displacement sensors, an n-shaped steel plate, a pile head fixing nut, a first fixing support, level pipes, a hydraulic jack, a first force transmission shaft, liftable supports, a counter-force device end plate, an oil inlet pipe, first L-shaped steel plates, a load sensor, second L-shaped steel plates, a third force transmission shaft and a second fixing support. The hydraulic jack is supported and fixed by means of cooperation of the first L-shaped steel plates arranged at the two ends of the hydraulic jack, the first fixing support and the corresponding liftable supports. The load sensor is supported and fixed by means of cooperation of the second L-shaped steel plates arranged at the two ends of the load sensor, the second fixing support and the corresponding liftable supports. The load sensor is connected with the counter-force device end plate through the third force transmission shaft. According to the mini pile horizontal static load test device and method, during the mini pile horizontal static load test, force transmission is completely horizontal, horizontal displacement of the pile end of a mini pile can be detected accurately, mounting and adjusting are convenient, the height of the supports can be adjusted, and the device and method are suitable for pile heads of any height and can carry out dual pile testing at the same time.