Geophysical and geochemical exploration work, all measuring points has its only location on land, in sea and air. According to the design requirements of work, the measuring points were marked by different ways in different stages. In the field observations, the measured points positioning by GPS (global positioning system) or DGPS (difference global positioning system) were marked by geodetic coordinate in geodetic coordinate system. In this paper, establishment and characteristics of geodetic coordinate system and common projective coordinate system, selection and application of projective coordinate system were described, but specific formulas were not involved.