Abstract: Portable GPS can position single point absolutely in the phase of pre-investigation and mineral prospecting, which can improve precision, reduce working intensity, and simplify work program.The portable GPS must be used according to the regulation and be tested in order to keep precision, including the control point choice, instrument parameter correction, precision test and consistency checking with different GPS equipments and then draw a conclusion of the GPS usage.The application effect in geochemical exploration is illustrated through field work examples.The GPS track can be used to check field work on the same day and draw the monitoring map and material map.Geology map can be drawn and survey grid can be layout by GPS and Mapgis.The assay discussed mainly about the details of the parameter setting, adjustment, accuracy and so on in order to ensure precision and quality of the GPS application to positioning of survey.