The invention relates to the field of dynamic capture systems in power training, and more particularly to an optical three-dimensional motion capture method and system. The method comprises the following steps that an infrared emitting and receiving device emits infrared rays at a predetermined frequency in a preset space in a three-dimensional space; for the currently emitted infrared ray, a handle that moves in the three-dimensional space receives and reflects the current infrared ray to the infrared emitting and receiving device; the direction that the current infrared ray is emitted to thehandle is opposite to the direction that the handle reflects the current infrared ray; a background system calculates the current position coordinates of the handle in the three-dimensional space according to the time point at which the infrared emitting and receiving device emits the current infrared ray and the time point at which the current infrared ray is received; and the background systemdetermines whether the handle is currently out of the preset range based on the current position coordinates, and issues an alarm if the handle is out of the preset range. The invention can ensure that the students are located in the virtual experiment environment in real time in the power training.