The invention discloses a method for simultaneously detecting residual quantities of oxamyl and oxamyl oxime in vegetable/fruits. The method comprises the following steps: (1) extraction: vegetable/fruit samples to be detected are taken, acetonitrile and NaCl are added, and homogenizing and centrifugation are carried out; (2) purification: an upper layer acetonitrile phase is taken and placed in a centrifuge tube containing a matrix solid-phase dispersion extractant, centrifugation is carried out, supernatant is taken, drying is carried out with nitrogen, volumetric flask preparation is carried out for a mobile phase, a 0.22[mu]m organic filter membrane is used for filtering, and a sample liquid is obtained; (3) determination and result calculation: HPLC-MS/MS is used for detecting the sample liquid, chromatographic peak area of oxamyl or oxamyl oxime is detected, the value is substituted into a standard curve, and content of oxamyl or oxamyl oxime in the sample liquid is obtained by calculation. The solid-phase dispersion extraction technology is used, the simple and rapid pre-treatment method is established, and detection limits of oxamyl and oxamyl oxime are 0.002mg/kg and 0.001 mg/kg respectively; the method has the advantages of simple operation, fast speed, accuracy, high sensitivity, and good repeatability.