Soil phytotoxicity studies were performed with different doses of creosote by means of the PHYTOTOXKIT test, using Sinapis alba, Lepidium sativum, Sorghum saccharatum as test plants. The obtained results indicate highly significant effect of the creosote dose, duration of soil incubation, type of test plant and period, after which the root length measurement was performed during the phytotoxicity index root test. The analysis of results indicates the highest sensitivity of Sorghum saccharatum to creosote and the highest correlation of results obtained with the aid of Lepidium sativum when measuring the root length after the first day the seeds are lined with the size of the dose. The proposed mathematical model makes it possible to predict the reaction of test plants on the size of creosote dose as well as to assess its amount in the soil based on the root phytotoxicity. These results allow for a significant simplification of the test and shorten its duration. This allows the modified test to be used for simple monitoring of not only the phytotoxicity but also the creosote residues during reclamation of contaminated soil.