Abstract: In the process of oil and gas exploration, the evaluation of geological reserves is a very important work, and the key of the evaluation of geological reserves is to grasp the relevant geological parameters.Volume method is a common method to calculate geological reserves.However, the geological parameters are uncertain, there are some deviations in the calculation of geological reserves by volume method.Probabilistic reserve estimation is based on probability theory, which regards reserve parameters as random variables varying in a certain range, and parameters are independent.The estimated result is a probability distribution curve of reserves(or a cumulative probability curve), estimating all kinds of geological reserves according to the prescribed probability value.In this paper, the parameters of coal seam thickness, gas content and single point abundance distribution are analyzed by probability method.By means of probability statistics, combined with a coalbed methane gas bearing area in Qinshui basin at the later stage of development, the geological reserves of coalbed methane under different risk values are estimated.According to the evaluation results, the CBM reserves under different risk values are given, to provide better technical support for exploration and development decision-making.