Abstract: The forces and the occurrence states of shale gas in various pore types are analyzed by different types and sizes of pores and by means of Lee potential?energy function. It is suggested that shale pores can mainly be divided into three types: organic pore, clay mineral pore and nonclay mineral pore, and each pore has its typical feature; the methane molecules in each pore are effected by dispersion force, some methane molecules near the pore walls are adsorbed by dispersion force, some are in free state when they are not effected by the force; with the increase of shale pore sizes, the proportion of area affected by pore wall is decreased and the adsorption ability of pores goes down; the adsorbed gas is mainly distributed in the pores less than 10 nm, the adsorption abilities of the organic matter and the clays with lots of micropores are higher than other minerals; in organic and clay pores, the shale gas exists by way of adsorbed gas and free gas, while in mineral pore, it does by free gas