Based on the adjacent matrix, a new principal quantum number topological index mX was set up：0X=Σ(δi)0.5， 1X=Σ(δi*δ\-j)0.5. The 0X, 1X values of 94 molecules for 13 series of compounds are calculated. It is found that 0X, 1X are correlated well with the retention indices RI of gas chromatography for these compounds .The results show that all the correlation coefficients are larger than 0.97. It has been demonstrated that the method possesses the advantage of easy computation and clear physical significance.