In context of atmospheric photochemical model,the photochemical ozone creation potential(I_POCP value) of NMHC species is studied under different NMHC/NO_x ratios.And the rule of I_POCP values of NMHC changing with time is discussed in the higher NMHC/N O_x ratio.The results show that the I_POCP values of NMHC species vary with the ratio of NMHC/NO_x and time-scale of photochemical reactions sys tematically.NO_x、alkenes、aromatics and aldehydes have higher reactivity and shorter lifespan,so its transportation distance is limited and mainly perf orming local pollution.Alkanes have lower reactivity and longer lifespan,so it can transport longer distance from its source.