An engine starting circuit used for providing enough voltage for ignition of a spark plug (10) when the engine is started and works. The engine starting circuit comprises: an ignition circuit (1) used for boosting a voltage accessed to the ignition circuit (1) to the ignition voltage of the spark plug (10); a magneto circuit (2) that is connected to the ignition circuit (1) by means of a first switch (k1); a direct current power source circuit (3) that comprises a direct current power source (32) and a second switch (k2), wherein the direct current power source (32) is connected to the ignition circuit (1) by means of the second switch (k2); an electronic control circuit (4) used for obtaining the working state of the engine and sending a control signal; a switching circuit that receives the control signal, and controls the ON/OFF of the direct current power source circuit (3) and the magneto circuit (2) by controlling the turn-on/turn-off of the first switch (k1) and the second switch (k2); and a starting motor circuit that comprises a starting motor (51) mounted on the engine, wherein the starting motor circuit is connected with the electronic control circuit (4) and receives the control signal to control the starting/stopping of the starting motor (51). By switching the magneto circuit and the direct current power source circuit, when the engine begins to be started, the present invention uses the direct current power source to provide the ignition voltage, so that it is ensured that the spark plug can obtain enough ignition voltage and can also be normally activated in a low temperature state; after the engine normally works, the direct current power source is changed to provide the ignition voltage for a magneto; and the present invention is environmentally friendly and energy-saving.