High concentration particulate matter (PM) has been a serious environmental problem in China and other developing countries. Electrostatic-based purification technology is a method to remove airborne particles, and can reduce the energy consumption of ventilation fans in buildings because of its low pressure drop. In this study, we developed a new pin-to-plate corona discharger with particle-free external air protection to prevent particles polluting the surface of discharge pins. By using an optical microscope, we observed a certain number of particles deposited on the non-protected (exposed pins) and few particles deposited on the protected pins after they operating for 3 weeks. We experimentally studied the long-term performances of the exposed and protected pins in single-pass PM removal efficiency and ozone production. The results showed that the protected pins produce less ozone and have higher breakdown voltage than the exposed pins. Experimental results indicated that the improved pin-to-plate corona discharger has better long-term performance and is safer than the exposed one. The results of the research can give an understanding of how to improve electrostatic-based purification technologies toward stable discharging for high removal efficiency of particles.