The aim of this research work is Synthesis of ZnO/SiO2 with Palash leaves extract nanocatalyst by green synthesis route. Palash leaves extract contain a broad variability of bio-molecules which act as capping and reducing agents and increases the rate of reduction and stabilization of nanoparticles. Nanocatalyst synthesized by this method are eco-friendly and cheap. No work has been found on Butea monosperma (Palash) leaves extract with ZnO nanoparticles. This research work synthesis of ZnO/SiO2 with palash leaves extracts nanocatalysts has been made by using green synthesis route. This synthesized nanocatalyst was used for removal of COD (mg/l) and polycyclic aromatic hydrocarbons as pollutants from petrochemical industrial wastewater. The synthesized nanocatalyst of ZnO/SiO2 with palash leaves extract was characterized using BET surface area, FEG-SEM, EDAX, XRD, and FTIR. Results show that we have synthesized ZnO/SiO2 nanocatalyst with BET surface area 160.23 m2/g and SEM micrograph shows the spot of nano range particles. From SEM test it has been found that we synthesized ZnO/SiO2 nanoparticles in the range of 3 to 35 nm and average particle diameter is 15.8nm. XRD and EDAX result show that we have found nanoparticles of SiO2 and ZnO. FTIR results show that Zn-O, Si-O-Si stretching have been found at 1004.95, 861.24 cm-1 for ZnO and 1270.17 cm-1 for SiO2 respectively. Results shows that optimum percent removal of COD (mg/l) and acenaphthene (polycyclic aromatic hydrocarbon) as pollutant are 70 % and 79% respectably at 0.5g/500ml catalyst loading, at 30oC temperature for 4h reaction time. In Future this catalyst can be used to remove other PAH and phenolic compounds from petrochemical wastewater under visible light also and other industrial wastewater can also treat by this catalyst effectively. Copyright © 2018 VBRI Press.