Abstract: The construction of the direction changing section is a method of measuring a geological section applied commonly in areas with complex topographic and geological condition.The geological section is generally constructed using the geometric construction method and projection method.The construction process is overlaborate with a big error.In the paper the author proposes an accurate calculation method by use of coordinates and its related expanded point constrction method,makes and innovation of the conventioned calculation of the thickness of strata and puts forward a universal formula of non deterministric selection.Besides ,he also discusses how to perfect the method of constructing a geological section.