Abstract: Objective To observe the changes of gap junctions structure in gastric cancer tissues, and to investigate the protein and mRNA expression of Cx43 in these tissues, then to provide new idea for the research on the mechanism of gastric cancer and new target for the drug treatment. Methods Transmission election microscope(TEM) was used to observe the changes of gap junctions in both normal tissues and gastric cancer tissues. We also used Western blot and PT-PCR technology to detect the expression of Cx43 in normal tissues and gastric cancer tissues. Results The gap junction ultrastructure of gastric cancer tissues had been destructed, and it was more serious with the worse differentiation. The expression of Cx43 protein and mRNA in normal tissues were higher than those in gastric cancer tissues(P<0.05). The expression of Cx43 protein and mRNA in well-moderately differentiated gastric cancer tissues were higher than those in poorly differentiated tissues(P<0.05). The expression of Cx43 protein and mRNA in stage Ⅰ/Ⅱgastric cancer tissues were higher than those in stage Ⅲ/Ⅳ(P<0.05). The expression of Cx43 protein and mRNA in gastric cancer tissues whose depth of invasion couldn't infiltrate serosa were higher than those could infiltrate serosa(P<0.05). The expression of Cx43 protein and mRNA in gastric cancer tissues without lymph node metastasis were higher than those with lymph node metastasis(P<0.05). The expression of Cx43 protein and mRNA had no relationship with age or gender(P>0.05). Conclusion The change of gap junction ultrastructure and the abnormal expression of Cx43 protein and mRNA have relationship with the development of gastric cancer, which provide a new direction for target therapy.