Cloud computing provides a new development direction for the geological software. The authors have used cloud computing technology to develop a web-based online grid data processing system that allows users to easily obtain data processing capabilities such as filtering, extension, and derivative calculation without installation. The tool uses a three-layer architecture, namely the presentation layer, the logic layer, and data processing service layer. The presentation layer is developed using web 2.0 front-end technology to provide user interaction interface and data visualization functions. The data layer encapsulates a series of grid data processing algorithms, which are used to process data-processing tasks submitted by users and response data processing results. This layer includes filter calculation, frequency domain upward continuation method, and differential iterative downward continuation algorithm and some other means. The logic layer connects the presentation layer and the data layer, and calls the required algorithm and returns the calculation result according to the data processing request submitted by the user. The authors tested the correctness of the tool using magnetic data from a synthetic model, and verified the cross-platform convenience of the tool by comparative study of this means on different computing platforms.