The present study was undertaken for phytochemical composition and antioxidant activity of bark, leaves and seeds of Chinese rain tree (Koelreuteria elegans). Total phenols in methanol extract of bark, leaves and seed cake were found to be 99.3 ± 1.2 mg GAE/g, 109.1 ± 2.5 mg GAE/g and 60.0 ± 0.1 mg GAE/g respectively. Total flavonoids in the methanol extract of bark, leaves and cake were found to be 26.9 ± 0.4 mg CAE/g, 36.3 ± 0.2 mg CAE/g and 10.0 ± 0.06 mg CAE/g respectively. Antioxidant activity of the extracts were determined by DPPH free radical scavenging method and was found to be 96% at concentration of 0.06 mg/ml in the bark extract and 95% at conc. of 0.07 mg/ml in the leaf extract and 93% at conc. of 0.07 mg/ml in the seed cake extract respectively. EC50 was 0.023 ± 0.002 mg/ml for bark extract, 0.022 ± 0.002 mg/ml for leaf extract and 0.025 ± 0.01 mg/ml for the seed cake extract respectively.