The invention relates to the fields of analytical chemistry and food safety, and provides a detection method of the residual amount of a plurality of macrolide veterinary drugs in casings. The detection method comprises the following steps of: extracting a sample with methanol or acetonitrile; purifying the obtained extracting solution by a C18 or Oasis HLB (hydrophilic-lipophilic balance) solid-phase extraction column, taking an acetonitrile-methanoic acid aqueous solution with the concentration of 0.15% as a mobile phase, and performing gradient elution by adopting a ZORBAX Eclipse C8 analytical column; and performing electro-spraying, separating by a cationic scanning mode and detecting the residual amount of seven types of macrolide veterinary drugs. The detection lower limit of the seven types of macrolide veterinary drugs is 20 mu g/kg. The recovery rates of spiramycin, tilmicosin, oleandomycin, tylosin, erythrocin, roxithromycin and josamycin are respectively 71.4-78.8, 75.7-85.6, 81.1-85.8, 78.9-83.0, 87.1-89.6, 83.7-85.4 and 75.6-81.8; and the indoor relative standard deviations for the recovery rates of the spiramycin, the tilmicosin, the oleandomycin, the tylosin, the erythrocin, the roxithromycin and the josamycin are respectively 7.7-11.1, 8.0-15.7, 10.5-16.4, 8.1-12.5, 10.5-12.4, 10.6-14.4 and 7.8-18.0. The detection limit, the recovery rate, the precision and the like meet the related requirements at home and abroad.