The invention provides a data reading method based on a distributed storage system, which comprises the following steps: receiving a read operation request sent by a client; counting the heat of the data to be read in the read operation request; judging whether the current operation is a read operation or not, and if not, continuing to receive a read operation request sent by the client; if so, determining whether the object data requested by the read operation exists in the pgcache, and if so, assembling the contents of the data to be read; if not, processing the read operation request by theOSD, and after the processing is completed, assembling the contents of the data to be read. Therefore, the method can effectively reduce the read delay, improve the data read speed of the distributedstorage system, and further improve the read and write performance of the whole system by caching some hot data on the main pg and carrying out the data aging and hot data updating in the pgcache intime with the data reading