The invention provides a water tank dish-washing machine and a cleaning method thereof. The water tank dish-washing machine comprises a water tank component, a bowl basket arranged in a water tank, awater inlet control valve used to inject water used for cleaning into the bowl basket, a pressure switch, and a controller. The water tank component comprises the water tank and a cup assembly. A washing cavity whose top is open is limited in the water tank. The cup assembly is arranged on the bottom of the water tank. A water passing cavity and an air chamber which are communicated with each other are limited in a cup. The water passing cavity is communicated with the washing cavity through a water through port. The pressure switch is connected with the cup assembly and is communicated with the air chamber, and the pressure switch is used to detect pressure in the air chamber. The controller is connected with the water inlet control valve, an ultrasonic assembly, and the pressure switch.The controller controls the water inlet control valve to open when a washing program is executed, and controls the water inlet control valve to close when pressure in the air chamber achieves a pressure threshold, and controls the ultrasonic assembly to operate, so as to perform ultrasonic cleaning on to-be-washed tableware in the bowl basket. Thus, cleaning effect of the ultrasonic cleaning is improved.