Lanthanum doped with copper oxide nanoparticles with size ranging from 20 to 100 nm and 2 μm in length were prepared by reacting copper nitrate with Lanthanum oxide. The structure of the nanoparticles was confirmed by scanning electron microscope (SEM) analysis. Photocatalytic activity of the fungicide azoxystrobin was investigated. Four different types of soil (sandy loam, loamy sand, sandy clay, and clay soil) were investigated for the decontamination effect of catalyst on the azoxystrobin residues in the soil. Under direct sunlight, the catalytic process was monitored at two different azoxystrobin concentration levels. The optimum concentration of catalyst (lanthanum doped copper-oxide) required for the decontamination was found to be 0.05 g/kg. Residues were quantified by ultra-fast High-Performance liquid chromatography method (UHPLC-PDA). Parameters, DT50 and DT90 were calculated from the dissipation data. In four soils, the reaction's pace displayed first order kinetics. The addition of Lanthanum doped with copper oxide nanoparticles contributed to significant photocatalytic dissipation of residues. Complete dissipation of the residues was confirmed by the ultra-fast high-performance liquid chromatography. The method maximum allowable Limit in soil is 0.01 mg/kg.