A measuring method was proposed to calculate the sequences of shielding angle and azimuth of any point in the shading region, and to eliminate the measuring error of shielding angle caused by the theodolite height, by using the synchronous data of shielding angle and azimuth of two points in the area. Therefore,it is possible to obtain the sunrise time and the day length of any point in the shading region graphically or numerically, with the apparent motion locus of the sun and the above calculation of the corresponding point.