Abstract: Objective:The purpose of this study was to compare treadmill and field test for energy cost during running and walking in adult males, to analysis the differences and establish the conversion formula.Methods:15 adult males on the treadmill and on the field complete 4.8 km/h, 6.4 km/h, and 8.0 km/h walking and running.The gas metabolism was determined using the Cortex MetaMax 3B.Results:1) The indicator of gas index, heart rate and energy cost were very different during running and walking.2) There is a linear correlation between two sets of data.3) ICC and Bland-Altman method between the two groups proved that there was a significant consistency and relevance in the data of two sets.Conclusion:1) There is significant difference between the energy cost of treadmill and field test.Only the direct field measurement reflects the true state of running and walking of daily life and physical activity.2) Established a conversion formula of oxygen consumption and energy consumption between treadmill test and field test by linear regression method, but the formula need to further for validation because of the small sample size.