The invention discloses an electricity-saving power supply circuit. When an output end is connected with a load and the load normally works, a first switching tube, a second switching tube are saturated and conducted, a relay normally works, and a normally open contact is closed so as to ensure normal power supply of a power supply loop; and meanwhile, a first capacitor is charged by the second switching tube, when a current of a load end is very small, a third capacitor is slowly charged, after first delay time, voltages at both ends of the third capacitor are risen to a certain voltage value, the second switching tube is cut off, due to a discharge effect of the first capacitor, the first switching tube can be continuously kept in a conducted state, and only by second delay time of delay, the first switching tube is cut off, the relay K1 is disconnected, the integral power supply loop is cut off, and power supply is stopped. Automatic complete turn-off of a power supply in a load endsmall-current state is implemented, automatic turn-off of the power supply is implemented, cost is low, and the circuit is simple in structure and high in reliability.