Abstract: In order to study the gas production potential of low-rank coal reservoirs,taking No. 4 coal reservoir of Dafosi Minefield in Binchang Mining Area as an example, the indexes of critical desorption pressure-reservoir pressure difference, critical desorption pressure-abandonment pressure difference, effective desorption quantity and desorption efficiency are quoted, and combined with the characteristics of low-rank coal reservoirs, such as low gas content, large thickness and good permeability, the numerical simulation software of coalbed methane is applied to low-rank coal reservoirs. Quantitative evaluation of reservoir gas production potential is carried out. The results indicates that the critical desorption pressure-reservoir pressure difference of No. 4 coal reservoir in Dafosi Minefield is 1.27 MPa, the critical desorption pressure-abandonment pressure difference is 0.76 MPa~1.26 MPa, the effective desorption quantity is 1.25 m3/t~2.35 m3/t，the desorption efficiency is 1.99~2.46 m3/(t×MPa),which is lower than that of medium and high rank coal reservoirs, but because of the thickness and permeability of No. 4 coal seam is large, the numerical model of extraction is drawn. It is proposed to show that the average daily gas production in 5 years is 965 m3, which has the gas production potential of CBM wells with industrial gas flow. The field single well drainage and production practice also verifies the reliability of quantitative evaluation results of No. 4 coal seam. The paper considers that the indexes of coal seam thickness and permeability should be included in the quantitative evaluation index system of low-rank coal reservoirs.