In underground coal mining, particularly room-and-pillar methods, the coal pillars play a significant role in roof stability. Due to the increasing dimension, the pillar bearing capacity also increases, but more coal remains as pillar and therefore the recovery of mining operation decreases. Therefore, determining the optimum pillar dimension based on technical, economical and performance parameters is momentous. In this paper, the coal pillar is designed by using the concept of ground reaction curve (GRC). For this purpose, the GRC for coal pillars is drawn and then the elastic and plastic zone of coal pillar behavior is determined. Based on elastic and plastic zone, different equations are presented to draw a pillar reaction curve and the process of coal pillar design based on GRC is explained. As a case study, this new technique is applied to study the coal pillar state in Tabas coal mine of Iran. The results show that the presented new approach is successfully used in the design of the optimum coal pillar dimension, and also determines the elastic and plastic behavior limit, which is important especially for the logical design of yield pillars.