The invention discloses a ground connection structure, an electric water heater and a control method, and relates to the technical field of water heaters. The ground connection structure is provided with a current detection device on a wire between a ground connection terminal and a ground connection electrode of an electrical appliance; a power supply circuit of the electrical appliance is in series connection with a switching circuit; and the current detection device is used for detecting the magnitude of currents on a ground connection circuit and controlling the switching circuit to be disconnected according to the magnitude of current. The ground connection structure judges whether leakage currents cause potential safety hazards to an electrical appliance and a user according to the detected magnitude of the current on the ground connection circuit; and if potential safety hazards exist, electricity supplied to the electrical appliance is switched off through the switching circuitso as to stop using the electrical appliance, therefore,the current in the ground connection circuit is prevented from being conducted to the electrical appliance, and the damage to the electrical appliance is avoided, or the life safety of the user is prevented from being endangered.