The invention discloses a laser-based inside-laser coaxial wire-feeding additive manufacturing system and a forming method. The laser-based inside-laser coaxial wire-feeding additive manufacturing system is formed by a laser, a wire feeder mechanism, a movement actuating mechanism, a molten pool shape monitoring feedback module and a system control module. After a part model is cut into slices, aninitial path is planned, input parameters and technological parameters in a technology database are compared, the molten pool temperature corresponding to technological parameters and input technology parameters under different feature structures is optimized, printing parameters and a robot code under an optimal path are generated, a high-speed infrared camera acquires molten pool shape parameters during the printing process and transmits to the system control module, the system control module compares the acquired molten pool shape data and the technology data of the technology database module, meanwhile, the molten pool temperature change is monitored, and the molten pool temperature is corrected through feedback-adjusting laser power and is monitored and feedback-adjusted in real time, so that the molten pool shape is uniform and consistent and the printing process is stably controlled during the printing process.