The invention relates to a multi-axial loading system and method, and belongs to the field of geotechnical engineering techniques. A locating sleeve is arranged on a rigid frame, a pipe barrel is positioned in the locating sleeve, a first piston and a second piston are positioned in the pipe barrel, expanding agents are filled between the pistons, an adjusting bolt is contacted with a first piston, a pressure sensor is positioned on the rigid frame, and a loaded body is arranged between the second piston and the pressure sensor. The loading method comprises the steps of arranging the pipe barrel vertically, arranging the first piston into the pipe barrel, filling the expanding agents, covering a plastic film on the assembled pipe barrel after tamping the expanding agents flatly, then arranging the second piston into the pipe barrel, transferring the pipe barrel arranged horizontally into the locating sleeve, arranging the loaded body between the second piston and the pressure sensor, screwing the adjusting bolt to enable the loaded body to be closely contacted with the second piston and the pressure sensor, wherein the expanding agents can push the first piston and the second piston axially along with the increase of the volume of the expanding agents, and the pressure sensor can record the numerical value of expansion pressure applied to the loaded body and transmits the numerical value to a load recorder.