Disclosed in the present invention is a method for preparing (S)-1, 2, 3, 4-tetrahydroisoquinoline-1-formic acid and derivatives thereof, comprising : using a raceme of a compound represented by formula (I) or a raceme of a salt of the compound represented by formula (I) as a substrate, and making a R-type isomer of the compound represented by formula (I) react under the catalytic action of oxidation dehydrogenase in the substrate to generate imide acid represented by formula (II); and converting the imide acid represented by formula (II) into an S-type isomer of the compound represented by formula (I) in the presence of piperidine acid reductase and a coenzyme capable of supplying hydrogen anions. The present invention is featured by mild reaction condition, strong stereoselectivity, high reaction efficiency, high conversion rate, etc.