The invention provides a magnetic torquer for a microsatellite and an assembly method thereof, and belongs to the field of lightweight design technologies and assembly processes of the magnetic torquer. The magnetic torquer comprises a left mounting rack, a coil, a magnetic core, a right mounting rack, a left insulating baffle plate and a right insulating baffle plate; the two ends of the magnetic core are connected with the left installation frame and the right installation frame respectively, the coil is wound on the magnetic core, a left insulation blocking piece is arranged at the connecting position of the magnetic core and the left installation frame, and a right insulation blocking piece is arranged at the connecting position of the magnetic core and the right installation frame; the magnetic core is made of permalloy meeting the national standard 1J85, and the coil is wound by a single-layer polyimide enameled wire in a multi-layer and multi-turn mode. The magnetic torquer is designed in a light weight mode, a magnetic core material with low quality and low residual magnetism in national standard products and a single-layer enameled wire with the optimal scheme wire diameter are selected, an optimal winding scheme is adopted through a multi-target recognition method, the design structure is reduced, the weight of the magnetic torquer is reduced to the maximum extent, the optimal design is achieved, and therefore the satellite launching cost is reduced.