The invention discloses a method for preparing conjugated linoleic acid by catalyzing conjugation of safflower oil by use of a modified molecular sieve. According to the method, the safflower oil is adopted as a raw material, then the catalytic reaction is performed by using the modified molecular sieve, and finally the conjugated linoleic acid is obtained by performing centrifugation and distillation purification. The method disclosed by the invention has the advantages of high catalytic efficiency, good stability, low production cost, and no pollution during production.