ZnO modified LaMnO3 nanocomposites were prepared using the sol-gel method. The prepared nanocomposite was synthesized in 4 variation of ZnO (1:0.1, 1:0.3, 1:0.5 and 1:1). The LaMnO3/ZnO nanocomposites were characterized using X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The LaMnO3/ZnO shows the orthorhombic structure of LaMnO3 nanoparticles and hexagonal wurtzite of ZnO nanoparticles. The photosonocatalytic activity of LaMnO3/ZnO was tested using methylene blue under the combination of UV or visible light and ultrasonic irradiation. The photosonocatalytic efficiencies performed that the present of ZnO could increase the degradation of MB. LaMnO3/ZnO nanocomposite with molar ratio 1:0.5 show the highest photosonocatalytc activity both under UV or visible and ultrasonic irradiation. Furthermore, the photosonocatalytic activity with combination of UV or visible light and ultrasound irradiation led to more complete degradation compared to use light or ultrasonic irradiation alone. The radical oxidative of the sample was examined by the addition of some scavengers and the results show that hole as the most active species to degrade MB under UV or visible and ultrasonic irradiation.