GeoPyTool is an open source application developed for geological calculations and plots, such as geochemical classification, parameter calculation, basic statistical analysis and diagrams for structural geology. More than acting as a link from raw data stored in Microsoft Excel ® (MS Excel) files to vector graphic files, GeoPyTool includes recently developed routines that have not been included in previous software, such as the calculation of the Ce (IV) /Ce (III) ratio for zircons as a method to examine the temporal evolution of oxygen fugacity in the magmatic source for igneous rocks, and the temperature calculator with titanium in zircon and zirconium in rutile. Besides these routines, GeoPyTool also allows users to load any figure from articles or books as a base map. As a Python-based cross-platform program, GeoPyTool works on Windows ® , MacOS X ® and GNU/Linux. GeoPyTool can do the whole process from data to results without the dependence of Microsoft Excel ® , CorelDraw ® and other similar software. It takes Excel ® XLSX and CSV (Comma Separated Value) as the formats of both the input data source files and the output calculation results files. The figures generated by GeoPyTool can be saved as portable network graphics (PNG), scalable vector graphics (SVG) or portable document format (PDF). Another highlight of GeoPyTool is the multilingual support, the official version of GeoPyTool supports both Chinese and English, and additional languages can be loaded through interface files. GeoPyTool is still in the development stage and will be expanded with further geochemical and structural geology routines. As an open source project, all source code of GeoPyTool are accessible on Github (https://github.com/GeoPyTool/GeoPyTool). Users with Python experience can join in the development team and build more complex functions expanding the capabilities of GeoPyTool.