Hole-drilling strain-gage method for measuring working strains in concrete structures has been discussed by tests. Pre-loading strain has been used to simulate the working strain in concrete structure, and model beams have been sued for drilling measurement tests in the lab. Some key issues of this work have been studied, such as strain gages selected, waterproof, data continuous transmission out of hole, etc., and the strain release curves have been obtained. On the basis of the work, the effects of drilling depth (h), hole diameter (d), original strain and the environmental temperature have been analyzed, and general laws of working strains measurement described by strain released rates have been obtained. These results have been successfully applied in the existing bridge inspection, and referred for reinforcement design and construction.