In order to study the mechanical properties of pesticide-contaminated soil, the unconfined compressive strength test was carried out on loess under different organophosphorus pesticide(glyphosate, glufosinate) contents, compaction degrees, moisture contents and curing time. In the meantime, the microstructural characteristics of contaminated soils were also explored. The results show that the unconfined compressive strength of the contaminated soil decreases with the increase of pesticide content, and the influence of glyphosate on the soil is similar to that of glufosinate. The unconfined compressive strength of the contaminated soil increases with the increase of compaction degree and curing time, but decreases and levels off with the increase of moisture content. Microstructural analysis reveals that pesticide intrusion into the soil does not change the mineral composition of the soil, but adsorbs on the clay mineral particles in the soil, and reacts with the mineral interlayer ions to reduce the interlayer column support. Therefore, the addition of pesticides makes the particles more fragmented, increases the number of large pores in the soil, disperses the particles and reduces the strength of the soil.