Investigates the joint managed inventory(JMI) problems of construction materials supply chain consisting of one general contractor and multiple sub-contractors. On the condition that short supply is not allowed，establishes the inventory cost model. Comparing the traditional independent inventory cost and that of supply chain JMI, proves that the total cost of the JMI is lower. Taking one general contractor and two sub-contractors for an example, studies the cost allocation of joint managed inventory, and verifies that using Shapley value method to allocate the cost, the shared cost of each participant in supply chain JMI is lower than that of traditional independent inventory.