Abstract: Under the optimal conditions for degradation of petroleum hydrocarbon by microorganisms,GC\|MS technique was used to monitor and analyze the degradation patterns of n\|alkanes in soil.The results showed that n\|alkanes have the fastest degradation rate among petroleum hydrocarbons;heavier n\|alkanes have slower degradation rate;tricosane shares the same degradation rate with the total petroleum hydrocarbons in the soil;the degradation rate of alkanes with carbon number less than 23 is greater than that of total petroleum hydrocarbons;and the degradation rate of alkanes with carbon number greater than 23 is less than that of total petroleum hydrocarbons.The degradation rates of C¹⁶～C²⁵ are biggest in the period from the beginning to the 6^th day,reach the minimum from the 7^th to 14^th day,and have the increasing trend afterwards.The degradation of the total n\|alkanes follows with the second order reaction kinetics law.