Hybrid CH3NH3PbX3 (where X = I, Br, Cl) is a hybrid organic-inorganic material with a perovskite structure and is sensitive to moisture, oxygen, UV light, light soaking, heat, electric field, etc. Among all these factors, thermal stability is one of the most challenging concerns affecting device stability, since it is hard to avoid a temperature increase during operation, leading to phase transition from tetragonal to cubic. Furthermore, the mechanism of phase change has been largely unexplored. In this work, we propose doping 2.5% SnCl2 into CH3NH3PbI3 in order to enhance its phase transition temperature from 57 degrees C to 90 degrees C, demonstrating amazing heating tolerance. The enhancement can be attributed to slightly modified interaction with the ions in the provskite crystal network. Surprisingly, upon comparison to their undoped counterparts, the samples with low concentration doping yields stronger intensity of light absorption and the efficient electron extraction. Herein, our results can provide an important step toward material engineering to address some of the key challenges facing perovskite based solar cells and other optoelectronic devices.