Hydrogenation of diesters to diols is a vital process for chemical industry. The inexpensive Cu+/Cu0-based catalysts are highly active for the hydrogenation of esters, however, how to efficiently tune the ratio of Cu+/Cu0 and stabilize the Cu+ is a great challenge. In this work, it is demonstrated that doped Ti ions can tune the ratio of Cu+/Cu0 and stabilize the Cu+ by the Ti-O-Cu bonds in Ti-doped SiO2 supported Cu nanoparticle (Cu/Ti���SiO2) catalysts for the high conversion of dimethyl adipate to 1,6-hexanediol. In the synthesis of the catalysts, the Ti4+-O-Cu2+ bonds promote the reduction of Cu2+ to Cu+ by forming Ti3+-OV-Cu+ (OV: oxygen vacancy) bonds and the amount of Ti doping can tune the ratio of Cu+/Cu0. In the catalytic reaction, the O vacancy activates C=O in the ester by forming new Ti3+��-OR-Cu1+�� bonds (OR: reactant oxygen), and Cu0 activates hydrogen. After the products are desorbed, the Ti3+��-OR-Cu1+�� bonds return to the initial state of Ti3+-OV-Cu+ bonds. The reversible Ti-O-Cu bonds greatly improve the activity and stability of the Cu/Ti���SiO2 catalysts. When the content of Ti is controlled at 0.4��wt%, the conversion and selectivity can reach 100% and 98.8%, respectively, and remain stable for 260 h without performance degradation.