Abstract: The present disclosure provides a method for in-situ monitoring of a full cycle of spatter formation, ejection, and falling in laser additive manufacturing. In a spatter formation stage, a paraxial multiocular high-speed photographing apparatus is used to provide a high temporal-spatial resolution, accurately collect spatial positions of spatters at each sampling time, and reconstruct a motion trajectory of the spatters in three-dimensional (3D) space. In an ejection stage, a coaxial monocular high-speed photographing apparatus is used to provide a long-term high temporal-spatial resolution and accurately collect and count an ejection velocity and angle and a motion trajectory of the spatters, and a photodiode monitors a radiation intensity and changes of the spatters. In a falling stage, a multiocular photographing apparatus is used to provide a high spatial resolution covering an entire powder bed and collect a distribution state of falling spatters.