The sensors of perovskite quantum dots (QDs) based on Pb have gained more popularity in sensing applications. However, severely restricts any more practical uses because of the toxicity of Pb. In this study, we created an efficient in situ method to make bone gelatin‐CsSnCl 3 QDs in 1‐allyl‐3‐methyl imidazole chloride ([AMIM]Cl), which were both very stable and environmentally benign. As a consequence, the relative photoluminescence intensity of bone gelatin‐CsSnCl 3 QDs retained over 96% in water for 55 h, showing negligible degradation. The oxidation of Sn 2+ in CsSnCl 3 QDs was effectively prevented. The interaction strength of carboxyl, amino, and long molecule chains in bone gelatin and CsSnCl 3 QDs was evaluated; the strongest binding force is between ‐COO − and CsSnCl 3 QDs; and the weakest is between long molecular chains and CsSnCl 3 QDs. Furthermore, bone gelatin‐CsSnCl 3 QDs demonstrated good selectivity and a low detection limit for Fe 3+ in aqueous solution (150 μM). The findings indicate that bone gelatin‐CsSnCl 3 QDs have a bright future in the realm of fluorescence sensing.