An ultraviolet survey of interstellar CO toward the bright stars had been made with ORFEUS mission Ⅰ and Ⅱ. In the range of 1086Å-1102Å, CO absorption line(1088Å) and $H_2$ absorption lines exist and only seven stars among about 100 show the CO absorption line. Fitting the spectrum gives the column densities of CO, each rotational level of $H_2$, and the kinetic temperature of molecular cloud. It is found that CO column densities are in the range $10^{13}-10^{15}cm^{-2}$ and show good correlation with those of $H_2$. The $CO/H_2$ ratio is about $2\times10^{-6}cm^{-2}$ for $N(H_2)＞10^{19}cm^{-2}$, and the $CO/H_2$ratio is about $4\times10^{-4}cm^{-2}$ for $N(H_2)＜10^{19}cm^{-2}$. CO column densities increase as the color indices, E(B-V), increase. So we can find that the abundance of CO is proportional to that of dust. However, It is not easy to find the relation between the CO column density and the fraction of molecular hydrogen to total hydrogen. Also, there is no correlation between CO column density and temperature.
