Physical activities are complex, which are affected by many factors including activities duration, intensity and frequency et al. Traditional physical activity evaluation principle is hard to differentiate miscellaneous physical activities well. The compendium of physical activities is a integrative physical activity coding system, which distinguish physical activity based on the activity objective, type and intensity and is an important tool to study physical activity level. This article introduces the evaluation principles of physical activity level and an update of the compendium of physical activities coding system.