The results of a new triple-channel separator with dual functions of fluid pumping and particle removal are presented in this paper. The separator was made through a MEMS fabrication process using only one photo mask. A valve-less micropump was connected to a triple-channel at a downstream position, and the oscillating flow in the micro-channel was produced by the micropump. An important characteristic of the separator is its oscillating flow, which produces two vortices at the trifurcate zone. These vortices served as obstacles to increase the flow resistance of the center channel. Based on the rotating direction of these vortices, the particles were driven towards side channels to achieve the removal effect. Micro-particle image velocimetry (μ-PIV) with an external trigger was used to measure the flow characteristics of the vortices. Streamtrace patterns were obtained at the trifurcate zone in a time period. Image processing was used to count the number of particles and to analyze the removal efficiency. The optimal removal efficiency (close to 100%) is obtained at a driving frequency of 1.5 kHz and a divaricated angle of 25°. This study indicates that the positions of the vortices provided improved removal performance with respect to the driving frequency of the PZT (piezoelectric zirconium titanate) plate and the divaricated angle of the triple-channel.