The observation of the gigapixel image is the current research hotspot and how to view the image in short time is a big challenge. So in this paper we present an on-line viewing system of the distributed gigapixel image. We construct the MPI programming framework and use the MapReduce data processing model to stitch the subgraphs distributed in the different servers. Based on the size and location of the region of interest (ROI), only the relevant subgraphs will be transmitted and processed. Utilizing our on-line viewing system, users can observe the ROI of the gigapixel image in short time.