single sensor of flow rate was utilized to reduce the complexity of calculation. The comparison between the current flow rate value and the prior value was used to search for the maximum power point and the duty cycle of switch of buck converter was adjusted accordingly. This algorithm has been implemented on a PIC16F877 microcontroller. The proposed technique was tested on a prototype system which is composed of a 12-watt solar cell and a 6-watt water pump. The experimental results showed that this technique could effectively search for the maximum power point with the efficiency of the maximum power point tracking 98.6 percent and 98.3 percent at solar radiation 350 W/m2 and 500 W/m2, respectively.