Photocatalysts based on titanium dioxide were used for the purification of contaminated soil polluted by oil. Commercially produced slurry of titanium dioxide was modified with barium, potassium and calcium. The experiments were performed under natural conditions in summer months (July and August), applying direct solar light, which occurs in Poland. The preparation of photocatalyst samples and the experimental results obtained from the photocatalytic oil decomposition in the soil are presented. The most active photocatalyst for soil purification was titanium dioxide modified with calcium.