The invention discloses a time domain reflection-based detection method for maintenance quality of early-stage concrete. The detection method comprises the following steps: preparing a concrete test piece at first and burying an exploration tube in the concrete test piece; in continuous maintenance date from pouring to hardening, measuring a plurality of groups of dielectric constants of the concrete test piece in each corresponding maintenance date by using a time domain reflectometer which is connected, through a cable, with a probe that is inserted into the exploration tube; calculating water content by using a drying method and a tool; calculating a coefficient in a function equation by using a least square method according to the function equation of the dielectric constants and the water content and determining a functional relationship between the dielectric constants of the concrete test piece and the water content; then determining a functional relationship between the strength of the concrete test piece and the water content; and in practical engineering, measuring the dielectric constant of newly-poured early-stage concrete by using the time domain reflectometer, calculating water content, and then according to target maintenance strength of the concrete, optimizing and adjusting maintenance conditions in real time and monitoring maintenance quality in real time. The detection method provided by the invention has the advantages of simple, convenient and rapid measurement, high precision and good stability.