Objective This paper is to investigate the diagnosis of MSCT on metastatic gastric cancer lymph node image, to conduct the contrast analysis with postoperative pathological results, and to provide theoretical reference for clinical diagnosis and treatment. Methods The method of controlled research was applied to conduct researches on 200 patients with gastric cancer admitted by the impatient department of the Hospital from June, 2012 to September, 2014, all patients were subject to multi-slice CT (MSCT) scanning examination, the number of lymph nodes, diameter and reinforcement degree were subject to the observation and analysis, and postoperative disease examination results were compared to evaluate the pros and cons of MSCT examination. Results The detection rate of MSCT examination hit 23.91%, 66.14% and 9.95% respectively according to three criterions for diameters of lymph nodes. The detection rate of reinforcement degrees hit 26.98%, 62.14% and 10.88% respectively, and there were not significant differences in inter-group data when compared to postoperative pathological results (P>0.05). Diagnostic sensitivity, accuracy and specificity hit 90.94%, 92.74% and 95.64% respective, and X2 =9.38, 7.22 and 4.06 were respectively satisfied when compared with postoperative pathological results (P<0.05). The inter-group differences were statistically significant. Conclusions (1) The visualization rate varies under different criterions when MSCT is applied to conduct the image determination and examination on metastatic gastric cancer lymph nodes. (2) MSCT imposes specific imaging manifestations on gastric cancer metastatic lymph nodes when the scanning examination is applied, delivering high clinical diagnosis. (3) Preoperative examination results may be used as theoretical basis for clinical diagnosis and treatment plan, throwing important guiding significance.