We present the design, fabrication and testing of a microfluidic multichannel resistive pulse sensor for high throughput counting of microparticles. The high throughput counting results from using multiple parallel microfluidic channels to analyze the sample. Detection is achieved by using frequency division multiplexing where a known and unique frequency is applied to modulate each microchannel and a combined measurement is made across a single pair of electrodes. Testing results using 30μm polystyrene particles demonstrate that the throughput of the multiplexed device is improved 300% over a single channel device. In addition, the AC modulation method reduces the polarization effect on the microelectrodes, and thereby allows for measurement of the actual particle sizes. The multiplexed detection principle can be extended to a larger number of channels to further improve the throughput, without increasing the external detection electronics.