Abstract: Hydrocarbon generation is a kind of chemical reaction and organic material in source rock forms fluid hydrocarbon.There are two types of chemical reaction systems:open system and closed system.The source rock becomes denser as burial depth increased, and chemical reaction system becomes closed system.Current generation theory is just a hypothesis that maturity of source rocks in open system matches hydrocarbon generation.However it is not happened in closed system.Maturity of source rock is progressively degraded without hydrocarbon generation in closed system; the organic material of source rocks formed another kind of solid organic material.In most cases source rocks are in semi-closed system and hydrocarbon generation is not much.Since faults and fractures formed by structural movements in short time connected source rocks and permeable beds,chemical reaction system changed from open system to closed system rapidly and caused excessive hydrocarbon generation in short time.This process was named as hydrocarbon generation formed by structural movements which means main hydrocarbon generated in the period of structural movements and each movement is related to a peak of hydrocarbon generation if several movements exist.The new theory can be applied to find new reservoirs from traps which was supposed to have past hydrocarbon generating period and the gas generation threshold was extended.