Sn-based composites are considered as one of the promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacities and suitable operation voltages. However, they suffer the huge volume change and unstable electrolyte/electrode interface during sodiation/desodiation, which causes structure collapse and serious capacity loss. In the past few years, great efforts have been made to ameliorate the performances of Sn by rationally designing electrode structures/components or optimizing electrolyte composition. Here, the underlying sodium-storage reactions in Sn are summarized based on the results from theoretical calculations and advanced characterizations. Then, the recent progresses of Sn-based composites, i.e., Sn-based alloys, Sn/C composites, and Sn oxides/sulfides, with various structures for SIBs are discussed in details. After that, how the electrolyte affects solid-electrolyte interphase and the electrochemical performances is shown. Finally, the future directions for the applications of Sn-based composites in SIBs are suggested. Hence, this review provides a comprehensive scenario about the applications of Sn-based composites in SIBs. It will benefit the future development of alloy-type anodes in SIBs.