Relationship between the molecular connectivity indices and adsorption coefficient (Koc) of nonpolar organic compounds was investigated based on molecular topology.Close linear relationship belween ¹x and logKoc of nonpolar compounds was revealed by the regressive analysis of ¹x and logKoc of 300 organic compounds. Calculation accuracy would be further improved as ¹x^v,²x and ²x^v were introduced into the model. Ffty five percent of the estimated error was within 0.2 log unit for 99 nonpolar compounds studied. A quantitative model was developed for estimating Koc of nonpolar organic pollutant based on molecular connectivity indices.