In order to improve the applicability, maintainability and the cooling efficiency of piezoelectric computer chip water cooling system, a computer chip water cooling system driven by combined piezoelectric pump was proposed. Initially, the output performance of the combined pump units in piezoelectric water-cooling system with different combinations (series/parallel), pump quantity and the relative position were tested and analyzed under 220 Vpp square wave. Subsequently, a research on water cooling efficiency of piezoelectric water-cooling system was conducted, based on the experimental results of combined pump units. The experimental results indicated that as the double pump units working in series combination, the performance of the working units located at the first and tail position (AD) was optimal with maximum output pressure (25 kPa) at a frequency of 30 Hz. When four pump units were working in series combination, the maximum pressure (23.5 kPa) and maximum flow (13.5 mL/min) were obtained at 35 Hz and 55 Hz, respectively. While double pump units were working in parallel combination, the performance of the double-working pumps which were located at the first (AC) position was relatively poor; When four pump units were working in parallel combination, the maximum output flow (22 mL/min) and maximum output pressure (12.6 kPa) were obtained at 50Hz and 60Hz, respectively, through switching of series/parallel and the pump quantity. It was found that different combinations and pump quantities could acquire different cooling efficiency. The driving parameters of the combined piezoelectric cooling system are obtained, which provide a novel approach for the effective cooling of computer chips.