3D Platelet EM, the full name of which is 3D Platelet Electron Microscopy, is a dataset for studying EM cell dense segmentation. The dataset contains two images of human platelets under a three-dimensional electron microscope, as well as instance segmentation and semantic segmentation of these two images. These data have been reviewed by NIBIB, do not contain PII or PHI, and can be publicly released. All files are in multipage uint16 TIF format, and the image voxel is approximately 40*10*10 nm.