Objective To detective KRAS and BRAF mutations in gastrointestinal stromal tumors (GISTs) and explore its significance in resistance of imatinib treatment. Methods Three hundred and eighty-one c-kit/PDGFRA mutation samples, 119 c-kit/PDGFRA wild type samples, and 19 pairs of samples before and after imatinib resistance from 519 patients with GIST were enrolled in this study. Polymerase chain reaction was used to detect KRAS exon 2 and BRAF exon 15 mutations. The survival data were evaluated in patients with KRAS or BRAF mutation. Results KRAS mutation was found in 2 cases (1.7%) of c-kit /PDGFRA wild type GISTs, the type of KRAS mutation was G12D and G12C, respectively. BRAFV600E mutation was found in 2 cases (1.7%) of wild type GISTs. No KRAS and BRAF mutations were found in the patients with the c-kit/PDGFRA mutation GISTs and pairs of GISTs before and after imatinib resistance. Two patients with KRAS mutation showed shorter progression free survivals for imatinib treatment. Two patients with BRAF mutation had longer recurrence free survivals. Conclusions Low frequency of KRAS or BRAF mutation only happens in wild type GISTs. KRAS mutation might be related to imatinib primary resistance, but not to secondary resistance.