[Objective] In order to explore the effect of heavy metals on the growth of freshwater green algae. [Methods] Chlorella vulgaris, which has been taken as an obvious indicator of water quality detection, was selected as the experimental material. CdCl₂·2H₂O and CrCl₃·7H₂O provided heavy metal ions, and different concentrations of Cr³⁺ and Cd²⁺ were explored effects of single and compound stress on its biomass, chlorophyll a and related antioxidant enzyme activities. [Results] With the continuous increase of Cr³⁺ and Cd²⁺ concentrations, the concentration of algae cells increased first and then decreased; the content of chlorophyll a first decreased, then increased, and then decreased, with a maximum of 1 mg/L single and combined stress value, and the toxic effect is Cr³⁺2+3++Cd²⁺; The content of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) related to the cell membrane of algae increases with the increase of the concentration of heavy metal ions; When the concentration of heavy metal ions is lower than 10 mg/L, it will promote superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the antioxidant enzyme system in algae cells, and it has inhibitory effect when it is greater than 10 mg/L. [Conclusion] The results show that under single or compound heavy metal stress, Chlorella vulgaris will fully mobilize enzymes related to stress resistance to maintain its normal growth.