Abstract: A formulaic solution，i.e.，derivative method，which is more simple and direct than that in the traditional textbook，is put forward for the virtual image coordinates of an object point in water，and the virtual image point and its trajectory equation with the changes of view are obtained. Thus the trajectory is made in the rectangular coordinate system. Meanwhile，a certain amount of interpretations are given to these results.

Key words: virtual image point, coordinate, formula, angle of view, trajectory