The invention discloses a weak security multicast rate allocation method based on network coding for multimedia data streams. The method comprises the following steps: obtaining a communication network where the multimedia data streams are located and parameters of the multimedia streams thereon, comprising a node set composed of a single server, all routers and a client receiving all data, a directed link set between the nodes in the node set, the capacity of each link, the number of data streams in the multimedia streams, a set of these data streams, and the weight of each data stream; expressing the communication network as a directed graph according to the obtained parameters; establishing a mathematical model of an optimal rate allocation method based on linear programming according to the directed graph; solving the mathematical model; and obtaining the maximum weighted data transmission throughput rate and a corresponding rate allocation scheme, that is, the transmission rate oneach link, of the multimedia stream transmission under a weak security condition. By adoption of the weak secure multicast rate allocation method, malicious intermediate routing nodes where the multimedia data stream transmission path in the multicast communication passes through met the weak security requirements, and the weighted throughput rate of the secure transmission is improved, thereby providing good security and improving the utilization rate of network resources.