A water-saving siphon toilet has a toilet body and a water tank, a eject water channel used for flushing the bottom of the toilet body and a brushing water channel used for brushing the washable surface of the toilet body are arranged between the toilet body and the water tank, and a siphon channel used for pollution is arranged at the bottom of the toilet body, and a first drain valve and a overflow pipe are arranged in the water tank, the eject water channel is isolated from the outside air, and reserved water is stored in the eject water channel for assisting flush the bottom of the toilet body next time. The eject water channel of the toilet body contacts outside air only at the water seal out of the eject hole when the toilet is at non-working states.