The invention discloses an HDFS-based virtual machine image storage system and a construction method thereof. The system comprises a virtual server, a management server, an HDFS storage node, a storage space manager, a read-write locating manager and an image data manager, wherein the storage space manager, the read-write locating manager and the image data manager are deployed in the storage management server. The method includes: the storage space manager is responsible of managing the disk organization form of storage space to finish storage of a great amount of virtual machine images; the read-write locating manager receives a virtual machine image operating command and randomly reads and writes specific images according to the metadata organization form; the image data manager is responsible of managing virtual machine image metadata and file content and organizes the image file content through the specific metadata structure. The HDFS-based virtual machine image storage system and the construction method thereof have the advantages that the HDFS has the limitation in supporting random file writing, a distributed fault-tolerance cloud storage mechanism of virtual machine image dynamic operation is achieved, reliability in data storage and access is improved, and the cost is reduced.