Abstract: Disclosed are an external-cavity-free low-threshold perovskite laser device and an application thereof. A gain medium is a perovskite material or a combination of the perovskite material and other materials. An ingredient of the perovskite is A?2An?1BnX3n+1, or ABX3, A? is an organic amine cation, A is a monovalent cation, B is a metal cation, and X is an anion; and a preparation method of the gain medium comprises dissolving A? X, AX and BX in a solvent to obtain a precursor solution of perovskite or a nanocrystalline, and the gain medium is prepared by a solution method. Or, the A? X, the AX and the BX are prepared by non-solution methods such as evaporation, vapor deposition, magnetron sputtering and solid-state reaction. According to the laser device in the invention, a resonant cavity does not need to be additionally designed and machined, so that compactness and integration of the device are improved.