The invention relates to a control method of ship and shore power grid connection and seamless switching. Power is directly compensated through electromagnetic torque Te to obtain an expected voltage;the frequency is further controlled through the relation between the rotational inertia J and the frequency response speed; and then a phase pre-synchronization process is added, so that grid connection and seamless switching are realized. The method has the advantages that the power and the voltage are detected through power and current detection devices, the three-phase voltage is obtained through a three-phase alternating current calculation law, and the shore power is used as an infinite power grid; power compensation can be carried out when the detected power does not meet the expected condition, the voltage obtained in the condition is compared with the expected voltage of the ship, the frequency and the phase position are obtained, and P-f control is carried out to adjust the frequency, the phase synchronization is adjusted under the condition that the frequency is equal, and the grid connection of the shore power of the ship can be stably realized; through the simulation of the characteristics of a virtual synchronous generator, the operability of shore power on the ship can be enhanced through the control of the ship PMS, and the probability of grid connection failure islowered.