Provided is a magnetic fluid electric generator taking low-melting-point gallium alloy as an electricity generation working medium. A main piston (5) and a main piston shaft (4) are arranged in a main hydraulic cylinder (1) in a coaxial mode. An upper auxiliary piston (7) and a lower auxiliary piston (8) are respectively arranged in an upper auxiliary hydraulic cylinder (2) and a lower auxiliary hydraulic cylinder (3) in a coaxial mode. Two ends of the upper auxiliary hydraulic cylinder (2) and two ends of the lower auxiliary hydraulic cylinder (3) are respectively communicated with the main hydraulic cylinder (1) and a magnetic fluid electricity generating passage (9). The magnetic fluid electricity generating passage (9) penetrates through a magnetic hole of a magnetic body (11). A pair of flat type electrodes (12) are tightly stuck to the inner wall of the magnetic fluid electricity generating passage (9) in a symmetrical mode, and the inner wall of the magnetic fluid electricity generating passage (9) is parallel to a field direction. Hydraulic oil (6) is filled into the upper portion of the main hydraulic cylinder (1) and the upper portion (2-1) of the upper auxiliary hydraulic cylinder (2). The hydraulic oil (6) is filled into the lower portion of the main hydraulic cylinder (1) and the lower portion (3-1) of the lower auxiliary hydraulic cylinder (3). The electricity generation working medium (10) is filled into the communicated space between the upper auxiliary piston (7) and the lower auxiliary piston (8), and the electricity generation working medium (10) is the low-melting-point gallium alloy.