The plasma discharge duration of EAST (Experimental Advanced Super-conducting Tokamak) is designed to be 1000 s, the time has exceeded 100 s at present. As the core subsystem, poloidal field power supply(PF) has nearly 200 signals to be stored. For every discharge, the amount of data is very large, ordinary database can’t meet the requirement of long pulse data storage. This paper uses HDF5 (Hierarchical Data Format) to store the long pulse data. HDF5 is a file format that can store different types of images and data. Using C interface of HDF5 to design a dataset with compound datatype, to realize real-time writing and reading, the primary discharge time is segmented and the data is written and read as chunks. Visualization tool Hdfview is used to view the dataset, and Qt is used to read HDF5 file and display waveform. It proves the correctness of compound datatype and chunk dataset, and the feasibility of writing and reading as chunks. Simple time test proves that writing and reading as chunks are efficient.