To investigate effects of Dragon’s Blood(DB),a traditional Chinese medicine,on blood coagulation and NO/iNOS level in myocardium and serum of rats in simulated microgravity for the first time,Sprague Dawley(SD)rats were randomly divided into six groups:(a)5-day control group,(b)5-day model group,(c)5-day drug group,(d)21-day control group,(e)21-day model group,and(f)21-day drug group.Blood coagulation and NO/iNOS level in myocardium and serum were examined after 5 and 21 days of simulated microgravity respectively.The results showed that blood of tail-suspended rats was in a hypercoagulable state that could not be converted with time extending.Conversely,DB changed these parameters towards normal level and the curative effects became better when tail-suspension lasted till the 21 st day.NO concentration of both myocardium and serum for two periods all increased markedly and DB could effectively reduce these increases except that of 21-day myocardium NO.Activity of iNOS increased markedly as early as 5 days and became more serious on the 21 st day,while DB showed preventive effect on the 21 st day.Western Blot analysis illustrated that the expression of iNOS in the 5-day model group increased significantly over the 5-day control group and the expression in the 5-day drug group dramatically returned to the normal level.The similar trend was observed on the 21-day groups without notable variances.The findings of this study can serve for the further use of Dragon’s Blood in space diseases. To investigate effects of Dragon’s Blood (DB), a traditional Chinese medicine, on blood coagulation and NO / iNOS level in myocardium and serum of rats in simulated microgravity for the first time, Sprague Dawley (SD) rats were differentiated into six groups: (a) 5-day control group, (b) 5-day model group, (c) 5-day drug group, -day drug group. Blood coagulation and NO / iNOS level in myocardium and serum were examined after 5 and 21 days of simulated microgravity respectively. The results showed that blood of tail-suspended rats was in a hypercoagulable state that could not be converted with time extending.Conversely, DB changed these parameters towards normal level and the curative effects became better when tail-suspension lasted till the 21 st day. NO concentration of both myocardium and serum for two periods all increased markedly and DB able effectively reduce these increases except that of 21-day myocardium NO. Activity of iNOS increased marked ly as early as 5 days and became more serious on the 21 st day while DB showed preventive effect on the 21 st day. Western Blot analysis illustrated that the expression of iNOS in the 5-day model group increased significantly over the 5-day control group and the expression in the 5-day drug group dramatically returned to the normal level. The similar trend was observed on the 21-day groups without notable variances. The findings of this study can serve for the further use of Dragon’s Blood in space diseases.