Background.　It　has　been　reported　that　circRNAs　are　differentially　expressed　in　a　wide　range　of　cancers　and　could　be　used　as　a　new　biomarker　for　diagnosis.　However,　the　correlation　between　circRNAs　and　gastric　cancer　(GC)　it　is　still　unclear.　Materials　and　Methods.　In　this　study,　by　using　real-time　quantitative　reverse　transcription-polymerase　chain　reactions　(qRT-PCRs),　we　detected　the　expression　level　of　hsa_circ_0001649　in　tissue　and　serum　samples　from　GC　patients.　Results.　We　found　that　hsa_circ_0001649　expression　was　significantly　downregulated　in　GC　tissue　compared　with　their　paired　paracancerous　histological　normal　tissues　(PCHNTs)　(P　＜　0.01).　We　next　analyzed　the　expression　level　of　hsa_circ_0001649　in　serum　samples　between　preoperative　and　postoperative　GC　patients.　We　found　that　its　level　in　serum　was　significantly　upregulated　after　surgery　(P　＜　0.01).　The　area　under　the　receiver　operating　characteristic　(ROC)　curve　was　0.834.　Moreover,　the　expression　level　of　hsa_circ_0001649　was　significantly　correlated　with　pathological　differentiation　(P　=　0.039).　Conclusion.　Our　test　suggested　that　hsa_circ_0001649　was　significantly　downregulated　in　GC　and　may　become　a　novel　potential　biomarker　in　the　diagnosis　of　GC.