In this experiment, relative particle size distribution was measured at inlet and outlet of the slit impactor using the Particle Sizer (Malvern) differently from the conventional experimental method. This measurement system has the advantage of obtaining the particle collection efficiency for various particle size easily and at one time compared with other method. The effect of jet to plate distance, Reynolds number on the characteristic impactor efficiency curves have been studied. In the result of this experiment, the increment of collection efficiency was observed as Reynolds number increases in the case of $S/W =\frac{1}{2}$ and the influence of S/W is more remarkable than that of Reynolds number on the particle collection efficiency.
