An optimization model for chemical production planning with optimal management of purchase and inventory was developed in this paper, based on the characteristics or the chemical industry. The objective of the model was to maximize the gross profit of a chemical enterprise while considering several constraints, such as material balance, chemical reaction balance, production capacity, product demand, raw material supply, inventory balance and inventory capacity. In the optimization model, a novel inventory management model was proposed to implement optimal management of purchase and inventory of raw and intermediate materials. In order for the above planning model to be applied in chemical enterprises to improve management level, a Graphic I/O Chemical Industry Modeling System (GIOCIMS) was developed. Tire proposed chemical production planning optimization model with optimal management of purchase and inventory was validated by two cases in which GIOCIMS was applied in a real world chemical enterprise. Results indicated that the proposed model was efficient for production planning optimization In the chemical industry.