The article presents the results of a study of an ecotoxicological characteristics dynamic effected by reagent treatment of ground oil sludge (OS), 7,92–18,67 wt% oil contented, using solutions of surface-active substances. The effectiveness of the treatment by different reagents at a mass ratio of oil sludge : reagent = 1: 10 (60°C and 120 rpm for 30 minutes) differs for different oil sludges. To analyze changes in ecotoxicological characteristics, samples of the original oil sludge and BOK-6 reagent treated were selected. The ecotoxicity dynamic has been studied by biotesting using standardized test cultures of different taxonomic affiliation (crustaceans, ciliates, bacteria, and higher plants). The ecotoxicity study using standard methods for the mortality of Daphnia magna crustacean and Paramecium caudatum infusoria showed that the original and treated oil sludge samples remained toxic to all test cultures, except for bacteria. However, shifts in the positive direction of the values of the «no observed effect concentration» NOEC10 are noticeable, which indicates a decrease in the toxicity of aqueous extracts after reagent treatment. It was established that oil sludge samples in all dilutions are safe for bacteria, since at all investigated dilutions the toxic limit in the Ecolum test system was not exceeded. The phytotesting was carried out by eluate and applicative methods using higher plants: radish Raphanus sativus L., white mustard Sinapis alba L. and oven Avena sativa L. – in the Phytoscan test system. The results showed a general decrease in the oil sludge ecotoxicity after its reagent treatment, as well as a higher sensitivity of the applicative method in comparison with the eluate method.