Abstract: It has characteristics in high precise and efficient of measure sound power with scanning methods. There are many kinds of measuring surface of scanning and so do scanning paths. They are among solving questions before proceeding scanning measurements. Rectangle surface is the easiest and most common measuring surface to determine sound power with scanning method, Several scanning paths on the rectangle surface are analyzed, It is shown that under the conditions of constant scanning speed and steady noise source, there exists many real scanning paths, though some of which are not easy to be realized, It is also shown that whether a scanning path is a real one is independent of the scanning speed, but the converging speed has bearing on the form of scanning paths which are straight line with circle rectangle, and sawtovth-shape scanning path is the fastest, the size of scanning surface is of little effect on scanning error.