The invention discloses a method for preparing bortezomib with (one)-cypress camphor serving as a chiral auxiliary reagent. The technological process includes that the (one)-cypress camphor and boronic acids in an organic solvent form boronic acid-(one)-cypress camphor esters; the boronic acid-(one)-cypress camphor esters are condensed and rearranged at a low temperature to obtain 2-chloro isoamyl boronic acid-(one)-cypress camphor esters; the 2-chloro isoamyl boronic acid-(one)-cypress camphor esters are aminated by lithium bis (trimethylsilyl) amide and removed protecting groups to obtain (one)-cypress camphor-(R)-1-amino-3-isobutyl-borate trifluoroacetic acid salt; the (one)-cypress camphor-(R)-1-amino-3-isobutyl-borate trifluoroacetic acid salt and pyrazine formyl-L-phenylalanine react under the existence of a condensing agent to generate bortezomib-(one)-cypress camphor esters; and the bortezomib-(one)-cypress camphor esters are hydrolyzed to generate bortezomib monomers and further generate bortezomib tripolymers.