To study the effects of different concentrations of salicylic acid on the heat resistance,we used Dendrobium officinale Kimura et Migo seedlings which is transplanted six months for the experimental material,observed and evaluated its heat tolerance under high temperature stress of different concentrations of salicylic acid-induced,dynamically determinated the activity of chlorophyll,soluble protein,soluble sugar,malonicaldehyde (MDA),free prolin (Pro) content,superoxide dismutase(SOD),peroxidase (POD),hydrogen peroxide enzyme (CAT) ascorbate peroxidase (APX),observed the dynamic trends and chose the best applied concentration.The results showed that,under high temperature stress environment,as the treatment time,the treated plants can effectively alleviate the high temperature damage,improve SOD,POD,APX activities in leaves,inhibit the increase of MDA,increase the accumulation of proline,soluble sugar and show soluble protein and significant differences between the different concentrations.In conclusion,under high temperature stress environment,with the stress treatment time,plants treated by different concentrations of SA can effectively alleviate the high temperature damage.When concentration of SA with 1.5~2.0 mmol·L^-1,the activities of SOD,POD,APX and CAT in leaf were significantly improved;When concentration of SA with 0.5~1.5 mmol·L^-1,the activities of CAT and APX in leaf were significantly improved;The concentration of SA with 1.5~2.0 mmol·L^-1 can effectively inhibit the increase of MDA,proline,soluble sugar and soluble protein accumulation,there are significant differences between the different concentrations.So show that salicylic acid can improve the heat resistance of D.officinale seedlings and 1.5 mmol·L^-1 concentrations can reach the best treatment effect and provide a favorable basis for the facility cultivation of D.officinale.