Cloud download service,as a new application which downloads the requested content offiine and reserves it in cloud storage until users retrieve it,has recently become a trend attracting millions of users in China.In the face of the dilemma between the growth of download requests and the limitation of storage resource,the cloud servers have to design an efficient resource allocation scheme to enhance the utilization of storage as well as to satisfy users\' needs like a short download time.When a user\'s chum behavior is considered as a Markov chain process,it is found that a proper allocation of download speed can optimize the storage resource utilization.Accordingly,two dynamic resource allocation schemes including a speed switching (SS) scheme and a speed increasing (SI) scheme are proposed.Both theoretical analysis and simulation results prove that our schemes can effectively reduce the consumption of storage resource and keep the download time short enough for a good user experience.