The invention relates to a phage antibody library which assembles an ScFv gene fragment between Restriction Enzyme cutting sites of SfiI and NotI of a pCANTAB5E carrier. The phage antibody library is characterized in that the ScFv gene fragment can be affinitive and enriched with antigens of 16-membered macrolide agricultural chemicals to form a soluble single-chain antibody and the phage antibody library is applied to immunoassay of pesticide residue. The phage antibody library has the advantages that the antibody with high affinity can be obtained without animal immunization, the test period is short, the antibody library is the phage antibody library which takes small molecular milbemycin oxime of a 16-membered macrolide generic structure as immunogen to construct, the antibody library theoretically can directly obtain a specific antibody library of 16-membered macrolide compound through screening, the screening flux is high, the efficiency is high, the specificity is strong, and the affinity selecting range is wide, so that the phage antibody library has wide application prospect in the aspects such as agricultural chemical antibody preparation, testing technique development and the like.