The invention discloses a fermentation method of conjugated linoleic acid and a strain used in method, and relates to a method in which linoleate isomerase is expressed by using a saccharomyces cerevisiae surface display system, and capable of catalytic synthesis of t10, c12-conjugated linoleic acid by using the linoleate isomerase. An expression vector containing a propionibacterium acnes derived linoleate isomerase gene (pai) is constructed and a saccharomyces cerevisiae strain containing the expression vector is obtained. After the induction culture, the linoleate isomerase is displayed and expressed in saccharomyces cerevisiae, and the linoleate isomerase is added into a buffer solution containing substrate linoleic acid for catalytic reaction to generate the t10, c12-conjugated linoleic acid. According to the method provided by the invention, the linoleate isomerase is linked to cytoderm of the saccharomyces cerevisiae by the microorganism surface display system, so that extracellular substrates and the linoleate isomerase can be fully contacted, the catalysis efficiency is improved, a single isomer with physiological activity can be obtained, separation and purification steps are simplified and the production cost is reduced.