Metal halide perovskite nanocrystals have emerged as excellent candidate materials for various optoelectronic applications due to their distinguished optoelectronic properties. However, suffering from instability under environmental conditions such as humidity, temperature and ultraviolet radiation restricts its further development and larger-scale application. In this study, we present a one-step method for fabricating composite thin films of formamidinium lead bromide and a lead-based metal-organic framework with enhanced stability. Meanwhile, the obtained composite films exhibited a low amplified spontaneous emission threshold of 12.3 μJ·cm−2 enhancing their potential for efficient optoelectronic applications, including light-emitting devices and lasers.