Due to their unique photoelectric properties, nontoxic tin‐based perovskites are emerging candidates for efficient near‐infrared LEDs. However, the facile oxidation of Sn2+ and the rapid crystallization rate of tin‐based perovskites result in suboptimal film quality, leading to inferior efficiencies of tin‐based perovskite light‐emitting diodes (Pero‐LEDs). In this study, we investigate the influence of commonly used solvents on the quality of the CsSnI3 films. Remarkably, DMSO exhibits a stronger interaction with SnI2, forming a stable intermediate phase of SnI2·3DMSO. This intermediate effectively inhibits the oxidation of Sn2+ and slows down the crystallization rate, bringing in lower defect state density and higher photoluminescence quantum yield of the prepared perovskite films. Consequently, the corresponding Pero‐LEDs achieve a maximum external quantum efficiency (EQE) of 5.6%, among the most efficient near‐infrared Pero‐LEDs. In addition, the device processes ultra‐low efficiency roll‐off and high reproducibility. Our research underscores the crucial role of solvent‐perovskite coordination in determining film quality. These findings offer valuable guidance for screening solvents to prepare highly efficient and stable tin‐based perovskites. To mitigate Sn2+ oxidation and rapid crystallization in Sn‐based perovskite, we investigated the effects of four different solvents on the crystallization and quality of CsSnI3 film. Compared with DMF, NMP, and GBL solvents, the use of DMSO‐based CsSnI3 films demonstrated efficient inhibition of Sn2+ oxidation and a noticeably reduced crystallization rate. This benefit can be attributed to the strong interaction between the S=O group of DMSO and Sn2+, as well as the formation of SnI2·3DMSO intermediate phase.