Abstract: The hemorheologic changes of 42 healthy pilots worked in three types of aircraft were observed. It was found that the blood viscosity and the hematocrit in pilot group at high sheer rate（225s-1） are significantly greater than in normal, erythrocyte aggregation and blood yield stress are lower than in normal, and significant changes in other hemorheologic parameters were not found. These resoults show that 1. there is influence of flying condition on hemorheologic parameters; 2. hemorheologic parameters have relation with the aircraft type, flight environment and dietary, but have no relation with the flight time; 3. it is suggested that we should be more careful to the realistic flight environment when pilots health protection is considered.