A liquid detergent supply for toilet includes a bottle, a lid and a flexible tube. The bottle has a connecting member for connecting with a water tank and an inner room with an opening for accommodating liquid detergent. The lid has an annular wall disposed in an end and a protruding portion in another end. A through channel communicated with the opening is disposed in the protruding portion. The flexible tube has an inlet end connected with the protruding portion to be in communication with the through channel and an outlet end penetrating into a floating block whose surface is level with the outlet end. The outlet end is tugged to float on water by a buoyancy of the floating block.