A method of oxidizing hydrocarbons in liquid phase is provided. According to this method, a liquid-phase oxidation reaction of hydrocarbons is carried out by using an organic compound capable of chelating metals as auxiliary agent, represented by formula (II), in the presence of an oxygen-containing gas and a transition metal catalyst. Accordingly, the conversion degree of the hydrocarbon is increased, and the overall yields of products are improved while the selectivity of catalytic oxidation reaction is still high.