The work aims to provide a theoretical basis for the design and structural optimization of spiral shell-tube heat exchanger by studying the effect of structural characteristics on heat transfer performance of spiral shell-tube heat exchangers. The flowing and heat transfer process of fluid in the spiral shell-tube heat exchanger was simulated in the Ansys FLUENT module of CFD software. Firstly, the tube diameter and shell length of the heat exchanger were changed without changing the total heat transfer area under the same boundary condition to investigate the effect of geometric parameters on heat transfer performance. Secondly, the temperature distribution contours of four spiral shell-tube heat exchangers with different structures (namely, single-tube-single-spiral, single-tube-double-spiral, double-tube-double-spiral, and internal-external-double-spiral) were compared to investigate the effect of spiral tube structure on heat transfer performance of the heat exchanger. The results indicated that, when the total heat transfer area remained unchanged, the heat transfer efficiency increased effectively with the decrease of tube diameter and the increase of shell length. Compared with single-tube-single-spiral heat exchanger, the outlet fluid temperature of single-tube-double-spiral heat exchanger declined approximately 9.74%, the outlet fluid temperature of parallel-double-spiral heat exchanger declined approximately 5.05%, and the outlet fluid temperature of internal-external-double-spiral heat exchanger increased by 10.11%. Based on these results, the heat transfer efficiency of spiral shell-tube heat exchangers will be improved by decreasing tube diameter, increasing shell length, and using internal-external-double-spiral structure in the process of designing and optimizing spiral shell-tube heat exchangers.