Abstract: Aimed at the problems in conventional plugging agents used in water production casing-damaged wells in Changqing Ansai oilfield, chemical plugging performance evaluations and matching system researches of slight expansion cement were conducted. A slight expansion cement system suitable for water production casing-damaged wells was developed. Laboratory experiments show this cement system has the characteristics of easily miscibility, well stability and effectively resident in plugging zone. Its micro-expansibility after solidification is benefit for preventing water producing that caused by contraction of cement paste in later plugging stage. It provides a new inorganic chemical plugging system to solve the plugging problems of water production casing-damaged wells in Changqing Ansai oilfield.