Objective To measure the activity energy expenditure(AEE) of healthy adults during level walking by using indirect calorimetry,and to analyze the characteristics and underlying influencing factors such as age and gender. Methods A total of 60 healthy adults aged 20-50 years (30 males and 30 femdes) participated in the study.All the subjects were divided into six groups by gender and age (the age span of each group was 10 years). The subjects were arranged to walk at speeds of 3.5,4.5,5.5km/h and run at 5.5,6.5,7.5km/h, respectively, on the treadmill. The resting energy expenditure ( REE ) and AEE were measured during walking and running at different speeds.There was a 5-minute rest among the test sessions. Results No difference in terms of AEE between the female and male at the same age ( P ＞ 0. 05 ). During 3.5km/h walking,AEE of 21-30 year-old females was lower than 31-40 yearold females and males( P ＜0.05 ) ;During 4.5km/h walking,AEE of 31-40 year-old females was higher than 21-30 yearold females and males and 41-50 year-old females; AEE of 21-30 year-old females was lower than 41-50 year-old males (P ＜ 0.05 ) ;During 5.5km/h walking,AEE of 31-40 year-old females was higher than 21-30 year-old females and males ( P ＜ 0. 05 ). During 6.5 km/h running, AEE of 31-40 year-old females was higher than 41-50 year-old females ( P ＜0.05), while during 7.5km/h running, AEE of 21-30 year-old males was higher than 41-50 year-old females (P ＜0.05 ). It was also found that the AEE of all groups except the 41-50 year-old females group was higher when walking at the speed of 5.5km/h than running at the same speed( P ＜ 0.05 ). Conclusions Age has more effect on REE and AEE than the gender. AEE of elder subjects is higher than that of the younger ones during walking, however, AEE of younger people increases faster than the elders during running. AEE of 31-40 year-old females is the highest in all groups both in walking and running. AEE in running is higher than in walking at the same speed.