In a power supply module of a linear actuator and a conversion assembly thereof, the power supply module includes a casing (10), a circuit control unit (11), and a conversion assembly (2). The casing (10) is provided with a dividing plate (102) for dividing the interior of the casing (10) into a first space (103) and a second space (104). The circuit control unit (11) is disposed in the first space (103), and the conversion assembly (2) is disposed in the second space (104). The conversion assembly (2) further includes a circuit board set (20) and a frame (21). The circuit board set (20) is electrically connected with an inductive element(A), a rectifying element(B) and a filtering element(C). The circuit board set (20) is mounted onto the frame (21) to form a modular structure.