Cross-border E-commerce has grown exponentially in the past decade in global market. To gain global competition in product-convergent markets, China¿s over 200 thousands cross-border E-commerce businesses have focused more on the service and cost control of supply chain downstream. In this study, we analyse three strategic cost control measures, summarise ten evaluation criteria for cost and develop an evaluation method for cost control using an extended COmplex PRoportion ASsessment (COPRAS) method, named L-COPRAS. This method is proposed to deal with uncertain or linguistic expression on strategic cost measures with varied weights to different alternatives. A case study of helping a Chinese E-commerce business to select strategic cost control measure on supply chain downstream is conducted. This study indicates that the proposed method is able to deal flexibly with uncertain information in supply chain downstream strategic cost evaluation.