Abstract: Waterflood development has been carried out in the Tahe Oil Field and the quality of injectedwater is the key for stable and increasing production.Taking Xidaliya waterflood station in the Tahe OilField as an example,the injected water which exceeded standard was analyzed.Combining lab evaluationand field experiment,water treatment agent was optimized and proved effective.The quality of offloadedwastewater was greatly improved,reaching "A2" level.