The embodiment of the invention provides a determination method, device and system for a virtual mouse position. The method comprises the steps that a laser spot position of a non-visible light frequency band on a projection screen, a boundary point position of a projection image on the projection screen and a screen display resolution of a computer projecting the image onto the projection screenare acquired; and the virtual mouse position is obtained according to the laser spot position, the boundary point position of the projection image and the screen display resolution of the computer. Through the scheme, the position of a laser pen spot relative to the projection screen can be calculated quickly and accurately, noise interference from visible light is avoided, the scheme has the advantages of a small calculated quantity, rapidity and accuracy, dual display of the laser pen spot and a mouser pointer cannot occur, and visual interference on field audiences is avoided.