Objective To evaluate the clinical value of 3.0T magnetic resonance imaging (MRI) diffusion weighted imaging (DWI) on evaluation effect of neoadjuvant chemotherapy in advanced gastric cancer. Methods 3.0 T MRI DWI examination was performed in 42 cases of advanced gastric cancer diagnosed by gastroscopy and pathology, including 32 patients were examined with DWI both before and after chemotherapy. Lymph nodes of gastric cancer lesions and display ability of stomach were measured, and the area of the apparent diffusion coefficient (ADC) values in normal stomach and tumors were compared. ADC values were compared in the same patients before and after neoadjuvant chemotherapy and analyzed along with postoperative pathological examinations. Results In a total of 40 patients who received 74 DWI examinations, ADC values in tumor and lymph nodes were significantly higher than those in normal tissue. The ADC value in tumors was (1.348 ±0.278) ×10-3 mm2/s, and in 12 cases of stomach lymph node enlargement was (1.329±0.188) ×10-3 mm2/s. However, the average ADC value of normal stomach was (2.081± 0.189) ×10-3 mm2/s with significantly lower DWI than that of the former (P< 0.001). After chemotherapy, the ADC value in tumors was increased, which was (1.572 ±0.261) ×10-3 mm2/s (P< 0.001). After neoadjuvant chemotherapy, 16 patients received gastric cancer radical prostatectomy, and postoperative pathological TRG ratings of tumor were decreased with different extent. Tumor cell density (TCD) before treatment with an average of 4.45 ×10-5 / px2, which was downgraduated to 2.48 ×10-5 / px2 after chemotherapy and surgery. Negatively correlation between TCD values and ADC values were observed. Conclusion MRI DWI examination can effectively detect advanced stomach cancer and the associated lymph node enlargement. Comparison of tumor morphology and ADC values in advanced gastric cancer before and after neoadjuvant chemotherapy has clinical value in prognosis.