The invention provides a toilet bowl water tank with a water leakage alarm function. The toilet bowl water tank is characterized in that a first liquid level sensor is mounted in a way that the first liquid level sensor is as high as the floating ball debugging liquid level of a floating ball water inlet valve so as to conveniently have immersion induction when the water tank is in a full water state, a second liquid level sensor is mounted at an overflow opening so as to conveniently have immersion induction when the water tank is in a water overflow state, and the upper and lower contacts of a contact type sensor are respectively mounted on a water discharge button and at the top end of a water discharge valve; when both the first liquid level sensor and the second liquid level sensor have immersion induction, a floating ball water inlet valve water leakage alarm signal is transmitted to an alarm; when the first liquid level sensor leaves water and loses induction and the contact type sensor keeps a noncontact state or when the contact type sensor changes from a contact state to the noncontact state and the first liquid level sensor does not have immersion induction in a preset time delay interval, a water discharge valve water leakage alarm signal is transmitted to the alarm. The toilet bowl water tank with the water leakage alarm function is scientific in design, simple in structure and capable of automatically judging water leakage conditions and effectively avoiding water resource waste.