According to the properties of light hydrocarbon in relation to environment, the modes of occurrence of light hydrocarbon can be divided into free state, dissolution state, physical adsorption state, chemical adsorption state and hydration state. Based on the distribution characteristics of light hydrocarbon of these five modes of occurrence which find expression in content and fabric, we can make discrimination and evaluation of corresponding strata and underlying strata. The composition and content characteristics of five modes of occurrence of light hydrocarbon contain abundant oil and gas information over all related oil and gas reservoirs in China.