The invention relates to a well repairing fluid, in particular to a well repairing fluid for a clastic rock reservoir. The well repairing fluid comprises a preparation base solution and additives, wherein the preparation base solution is formation water or a mixed solution of formation water and surface water; and the additives include a viscosity increaser, a corrosive inhibiter, a stabilizer and a sterilizing agent. According to the technical scheme provided by the invention, the well repairing fluid has the characteristics of high raw material compatibility, high compatibility with stratums, high temperature resistance, high mineralization degree, easy and practicable field preparation process and capability of meeting the requirement of protection of the reservoir.