The invention discloses a method for preparing 1,6-adipaldehyde by selective oxidation of cyclohexene. The catalyst is a cobalt complex of isosteviol derivatives. The method comprises the following steps: adding solvent, cyclohexene, Catalyst, co-catalyst, feed oxygen, keep the pressure of the reactor at 0.2~0.6MPa, the reaction temperature at 120~170°C, and the reaction time at 60~300 minutes to obtain 1,6-adipaldehyde. Compared with the existing method, the present invention, the free radical produced by the decomposition of tert-butanol peroxide reacts with oxygen to generate oxygen free radical, and the cobalt complex of the catalyst isosteviol derivative interacts with the double bond in cyclohexene It has higher reactivity, and the activated double bond reacts with oxygen free radicals to generate 1,6-adipaldehyde; the invention is environmentally friendly, and has good selectivity and high yield of 1,6-adipaldehyde.