This paper focuses on the appropriate selection of suppliers and assigning order quantities to them. This problem contains multiple objectives and their related constraints and utilizes fuzzy decision making in its solution approach. In the proposed model, goals, constraints, variables and coefficients are all fuzzy. It is shown that with the application of the fuzzy methodology, the multiy objective problem is converted to a single one that can be solved easily.

The strong competition in today's global markets and huge customer attention to factors such as price, quality, time delivery and product variety has caused the investors to focus on supply chain management. In this regard, selecting the choosing and determining the quota of each one is one of the most important and crucial decisions that not only is responsible for supplying the parts, but also accountable for maintaining the organization in the competitive environment. This paper is devoted to determine the optimal order of each product in a multi-objective and multi-period problem. The considered multiple objective functions include minimizing total purchase and order costs, transportation costs, percentage of returned and delayed products, also maximizing the total reliability of selected suppliers according to the necessary of supplying for each product. Due to the existence of unsustainable situation in the real world, in this paper the sustainable approach is introduced to create robust result.