Abstract:More than 95% of low permeability reservoir in Jilin Oilfield use the development way of injecting water, and injected water are mostly recharged water, therefore, it is necessary to study water quality and improve water quality,so that the oil recovery can be enhanced. In this paper, Fang 44 and Fang 68 blocks of bamiantai Oilfield are as exemples for the study of reservoir, to analysis the current status of the injected water , compatibility with formation water and the sensitivity with formation and the impact to the reservoir, analysis comprehensively injected water damage from the combination of external factors and internal factors and give suggestions for improvement of water quality.