Abstarct: The quality of life on earth is closely related to the quality of the environment. Soil is one of the most important and valuable sources of nature. Soils have always been exposed to many pollutants, among these contaminants we can name oil, gasoline and so on. Today, with increasing population of the world, another pollutant is the waste from the use of detergents that are widely introduced into the environment through wells and sewage leakage pipes and they can impose a lot of negative effects on it. These pollutants can, in addition to environmental destruction, also affect the geotechnical properties of the soil and cause to reduce the soil bearing capacity and resistance. Hence, the study of resistance behavior of soil against these pollutants is considered essential. In this research, the effect of these detergents on the shear strength of the soil has been investigated. Soil used in this research is CL and direct shear test and unconfined compression test was done. These experiments were carried out on non-additive samples and also samples with 2, 3 and 4% detergent and their shear strength was compared with the shear strength of non-additive specimens during one day, one week, two weeks and four weeks. In the test of unconfined compression strength that performed on one-day samples Compressive strength and non-drainage cohesion were reduced by increasing the amount of enzymatic detergent. Direct shear test results also showed a decrease in resistance and a change in the shear strength parameters of the tested soil and by increasing the detergent content, soil cohesion decreased as compared to non-additive samples. These changes have increased over time as the cohesion reduction for a 4% additive sample was 14% higher than the non-additive specimen on the first day, it reached 54% on the fourth week.