Abstract: The geological block method is the most important and commonly used method in coal resources/reserves estimation. However, the geological block does not have concrete definition in related norms and regulations. Different method of block division gives different results in resources/reserves estimation. According to the actual production, this paper analyses quantitatively the errors of different division methods, and conducts quantitative evaluations. Through analyses and determination of the influencing factors of errors, the best division method has been put forward, which has important realistic significance for the improvement of the accuracy of coal resources/reserves estimation in coal field investigation.