The work aims to take the inventory management of two commonly used building steels and cement materials stored in the same warehouse and supplied by the same supplier as the research object to save the management cost of materials in engineering construction industry. By analyzing the situation where the contractor purchased materials, the supplier and the contractor shared information based on cooperation. The optimization model for the combined inventory cost of two materials and two-echelon was established and the optimal solution of the engineering example was obtained by the particle swarm algorithm to verify the effectiveness of the research method. The ordering strategies of different materials had great influence on material inventory cost in construction supply chain. Mathematical model could give appropriate ordering strategies to satisfy the lowest system cost requirement, save costs and improve the overall competitiveness of construction supply chain. The research has enriched the theory of construction supply chain management and inventory management theory of engineering materials and also has guidance significance on material purchasing in the practice of project construction.