Circular RNAs (circRNAs) are a new class of RNAs， and many studies have identified thousands of circRNAs in tumor cells. Fibronectin type III domain-containing protein 3B (FNDC3B) circular RNA (circFNDC3B， circBase ID: hsa_circ_0006156) circularizes with exons 5 and 6. Gibson Assembly DNA technology was used to construct a circFNDC3B expression vector without a splice site and restriction enzyme site. We showed that circFNDC3B increased migration and invasion in gastric cancer (GC). Ectopic expression of circFNDC3B reduced the level of E-cadherin protein to promote the epithelial-mesenchymal transition in GC. RNA immunoprecipitation assays and RNA pull-down assays confirmed that circFNC3B increased CD44 expression， which was associated with cell adhesion， via the formation of a ternary complex of circFNDC3B-IGF2BP3-CD44 mRNA. These results indicated that circFNDC3B was associated with the degree of malignancy to highlight the specific characteristics of cell invasion.