In this paper，we used Dendrobium officinale protocorm as materials and studied the impact of low temperature (4 ℃) ,exogenous NO (NO donor SNP),NO scavenger (cPTIO) and nitric oxide synthase inhibitors(PBITU) on NO content,the sucrose synthase (SS) activity,and the content of polysaccharide,sucrose,fructose,glucose in D.officinale protocorm to clear the relationship between low temperature and endogenous NO in the course of polysaccharide synthesis.The results showed that:(1) Under the low temperature (4 ℃) treatment,the NO content significantly increased,the SS activity enhanced and the content of sucrose,fructose,glucose and polysaccharide increased in D.officinale protocorm.SNP(0.5 mmol·L^-1) treatment had the similar effect to the low temperature (4 ℃) treatment;under the low temperature (4 ℃) treatment,the SS activity and polysaccharide content increased after a lot of NO produced,sucrose accumulated earlier than fructose and glucose.(2) 4 ℃+SNP treatment could significantly improve the SS activity,and the content of NO,sucrose,fructose,glucose,polysaccharide in D.officinale protocorm.They were significantly higher 68.04%，96.20%，60.69%，45.64%，66.90% and 67.03% than that of control group,and the effect was better than that in low temperature (4 ℃) or SNP separate treatments.(3) PBITU could partially inhibit NO production in D.officinale protocorm which induced by low temperature (4 ℃) and the inhibition rate was 77.15%;it also inhibited the promotion of the SS activity,polysaccharide synthesis and the accumulation of sucrose,fructose,glucose in D.officinale protocorm which induced by low temperature (4 ℃).(4) Under SNP+cPTIO and 4℃+cPTIO treatments,the SS activity and the content of sucrose,fructose,glucose,polysaccharide and NO in D.officinale protocorm had no significant difference with the control group.Studies had shown that the low temperature and exogenous NO could promote polysaccharide synthesis in D.officinale protocorm,and low temperature induced NO production,the SS activity exaltation and polysaccharide content addition were associated with NO production.In D.officinale protocorm,NO is a necessary signal molecule for its polysaccharide synthesis.