An aerosol generator using spark discharge has applied to nanoparticle production. However, some by-products such as ozone, nitric oxide and nitrogen dioxide were simultaneously generated with particles in air. In this study, the generation characteristics of byproduct gases were investigated in terms of the air flow rates and the applied discharge power in spark discharge. The particle size distribution was measured using a SMPS system to observe the effect of gas absorption on silver nanoparticles. The results showed that NOx concentration increased linearly with discharge energy. However, ozone concentration increases with discharge energy in a low energy region, but decreases adversely with discharge energy in a high-energy region, which NOx concentration increases steeply in comparison of ozone concentration.