A novel modular electromagnetic actuator for micro-nano satellite application is proposed in this article. This actuator is combined with two functional units. The permanent magnet connection unit is used to realize the static connection of two micro-nano satellites with no power loss. The electromagnetic separation unit is used for the separation motion and transposition motion. Different magnetization types and topologies for these two units are compared. The attractive force characteristics for the permanent magnet connection unit are analyzed, and the attractive force ratio is used as an index to choose the proper magnetization type. For the electromagnetic separation unit, the repulsive force per mass is an important parameter for selecting a good topology. To suppress the magnetic field interference, the magnetic shielding structures are also designed. The results are based on 3D finite element calculation. Finally, the prototype of two cube frames with the proposed electromagnetic actuator are manufactured, and they perform well in tests, which verifies the related analysis and design.