This paper reports a novel lab-on-a-chip device that performs fluorescent particle counting by coupling the electrokinetically-induced pressure-driven flow and a miniaturized dual-wavelength fluorescent detection method. A novel L-shaped PDMS microchannel bonded on a thin glass slide is used to transport the particles. The dual-wavelength fluorescent detection system can count two different fluorescent particles simultaneously. Good agreement is achieved between the results obtained by the microfluidic chip device and the results from a commercial flow cytometer.