Abstract: In order to explore methodology for improving the resistance of pea primary roots to H₂O₂ stress, physiological characteristics of pea primary roots were studied using a pea variety “Longwan 1” treated with Ca²⁺ under H₂O₂ stress. Several physiological indexes like the curvature rate and root activity of pea primary roots were measured using physiological and biochemical methods. Some other indexes like the relative membrane permeability of primary roots, the concentration of malondialdehyde (MDA) in primary roots, the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) enzymes were also measured. The normal growth of pea primary roots under 80 mmol/L H₂O₂ stress was obviously inhibited. However, the inhibitory effect on root growth was reduced and the root activity was restored after treating with Ca²⁺. The MDA content decreased 37.32% compared to controls after treatment with 10 mmol/L exogenous Ca²⁺. The activities of four enzymes including POD, SOD, CAT and APX were enhanced and reached 51.946 U/(mg·min), 865.174 U/g FW, 1.9739 mmol/(L·g·min) and 2.569 μmol/(L·g·min), respectively. In summary, Ca²⁺ (10 mmol/L) significantly alleviated the damage to pea primary root cell membranes caused by H₂O₂ stress, reduced membrane permeability and promoted the antioxidant capacity of pea primary roots for stress resistance.