The physiological biochemical mechanism of heat stress Potentilla fruticosa was investigated through measuring the changes of physiological and biochemical indicators in leaves of the 2-years old P.fruticosa under the conditions to 6 d high temperature stress (42 ℃ from 9:00 to 15:00 and 30 ℃ during the rest time of each day) and 1 d recovery (Control,30 ℃ from 6:00 to18:00 and 20 ℃ during the remainder time of each day).Results showed that the membrane permeability,the contents of MDA,soluble sugar content and free proline content increased gradually,while the activity of SOD decreased,the activities of POD,CAT and APX first rose and then declined with the high temperature stress.All the indicators under the heat stress were significantly higher than that of control.However,the membrane permeability had no significant difference with control.All the indicators following 1 d recovery were almost same with control.P.fruticosa could increase the adaptability to heat stress by increasing the contents of osmoregulation substances such as soluble sugar and proline.In addition,P.fruticosa would improve the resistance to heat stress by increasing the activities of antioxidases such as POD,CAT and APX to remove the excess H₂O₂ and active oxygen to maintain the dynamic balance of generation and removal of reactive oxygen of cells.