The invention relates to a preparation method of (S)-(+)-3,4,8,8a-tetrahydro-8a-methyl-1,6-(2H,7H)-naphthoquinone. According to the preparation method, an L-proline derivative is used as a chiral catalyst and microwave radiation is introduced into chiral preparation of the (S)-(+)-3,4,8,8a-tetrahydro-8a-methyl-1,6-(2H,7H)-naphthoquinone for the first time through asymmetric Robinson cyclization reaction under conventional conditions or microwave irradiation conditions. Under proper power, an L-prolinamide type catalyst can keep excellent catalysis performance and the catalysis reaction time isshortened; compared with room-temperature stirring conditions, the synthesis efficiency is greatly improved. The molecular collision is aggravated through the microwave radiation and an intermediatecan more easily pass through an energy barrier to form a transition state, so that the reaction time is remarkably shortened, the preparation efficiency of the (S)-(+)-3,4,8,8a-tetrahydro-8a-methyl-1,6-(2H,7H)-naphthoquinone is greatly improved and the synthesis period is shortened. The method is low in cost, simple and rapid, high in yield and good in stereoselectivity.