This study was carried out to investigate the air pollution in Hwasoon Nulitjae tunnel for two months, from August 1992 to September 1992. The total suspended particles were collected by high volume air sampler at inside and outside of Hwasoon Nulitjae tunnel, of which major water soluble component and heavy metalic element were analyzed. Size distribution and respirable mass fraction of aerosol at inside were measured by filters on nine stages Andersen air sampler. The average concentration of TSP at inside was 657.57 $mu$g/m$^3$, which appeared about 9.2 times as high as that of 71.47 $mu$g/m$^3$ at outside. The decrease effect caused by using new tunnel was 31.2%. As a result of correlation analysis between concentration of TSP at inside of Hwasoon Nulitjae tunnel and that at outside, correlation coefficient was 0.713. The average concentrations of SO$_4^{2-}$ , NO$_3^-$, CI$^-$ were 43.02 $mu$g/m$^3$, 19.86 $mu$g/m$^3$, 4.96 $mu$g/m$^3$, those of NH$_4^+$, Na$^+$, K$^+$ 1.42 $mu$g/m$^3$, 4.45 $mu$g/m$^3$, 2.89 $mu$g/m$^3$ and those of Ca$^{2+}$, Mg$^{2+}$, Pb$^{2+}$ 3.92 $mu$g/m$^3$, 2.27 $mu$g/m$^3$. 1.52 $mu$g/m$^3$, respectively. It was estimated that mass fraction rate of respirable particle at inside was about 84.54% of aerosol. The average concentration of suspended particle to be collected by Andersen sampler was 478.90 $mu$g/m$^3$, this was about 72.8% of that by high volume air sampler.