Organic matter abundance of quaternary source rock of biogenic gas in eastern Qaidam basin is the key factor controlling biogenic gas resource in the area.By redesigning measurement processes,the assessment method of source rock for biogenic gas is established.The content of dissoluble organic matter in quaternary source rock of biogenic gas is about 2.6 times than that of insoluble organic matter.So most of organic matter in Qaidam basin appear as dissoluble form.Based on the special existing form of immature source rock of biogenic gas,the assessment system of organic matter abundance for quaternary source rock of biogenic gas in Qaidam basin is suggested.Appearance of giant amount of dissoluble organic matter in the quaternary source rocks illustrates that there still is methane generation in the area,and abundant organic matter in source rock provides a resource guarantee for biogenic gas exploration.