We present a simultaneous electrical and optical detection of particulate matter (PM) based on microfluidic chip for label-free and fast detection. The microfluidic system consists of the filters area for screening the large particles, which allows to pass through only particles smaller than 2.5μm, and the sensing area for detecting the particles using DC electrical measurements. As PM2.5 passed the cross-junction area, the disturbing electric fields would lead to fluctuating electric current in the detection circuit unit. Our measurement system has dynamic range from 200 nm to 2.5 μm. Furthermore, the amplitudes and the dwelling time of signals depended on the size of particulate matters that mean we would discriminate PM2.5 size in the range of millisecond (1-10 ms). Our system can detect a single particulate matter, which is applicable to count the number of PM2.5 for medical diagnostic, since the number of PM2.5 are found to be associated with several diseases.