A solenoid valve includes a coil housing, a coil barrel and an actuator. The coil barrel is mounted in the coil housing, is coiled with multiple coils, and has a valve gate formed on a bottom of the coil barrel. The actuator is moveably mounted in the coil barrel and has a piston, a magnetic shaft, a spring mounted between the piston and the magnetic shaft, and a sealing pad abutting the piston. The actuator is driven by the coils to move the piston. The piston has two notches being able to break a vacuum state, and can be pushed upward easily and efficiently to save electricity.