Sand culture experiment were carried out to study the effects of PEG pretreatment on physiological characteristics of Lolium perenne seedlings under salt stress and cadmium stress. The experimental seedlings were dealt with 0%, 5%,10%,15%,20% and 25% (the corresponding water potential was 0, -0.05, -0.15, -0.30, -0.50 and -0.77 MPa, respectively) PEG-6000 pretreatment nutrient solutions, respectively, and then the seedlings were cultured separately by stress solutions containing 150 mmol/L NaCl and 10 mg/L Cd²⁺, respectively. Then the leaf chlorophyll(Chl)content, activities of antioxidant enzyme (such as catalase (CAT),superoxide dismutase (SOD), guaiacol peroxidase (POD) and ascorbate peroxidase (APX)), contents of osmoregulation substances, such as proline, soluble sugar and malondialdehyde (MDA) in leaves were determined. The test results showed that the 15% (-0.30 MPa) PEG pretreatment under the salt stress and the 10%(-0.15 MPa) PEG pretreatment under the Cd²⁺ stress could effectively increase the leaf chlorophyll contents of L. perenne seedlings, reduce the contents of MDA and proline, increase the content of soluble sugar and increase the activities of antioxidant enzymes. The above results showed that the L. perenne dealt by PEG pretreatment under stress was regulated by various physiological and biochemical factors. The dynamic changes of physiological indexes were important regulatory mechanisms for L. perenne in respons to stress, which reflected its adaptability to stress and its cross-adaptation ability under various stresses.