The time-domain reflectometry (TDR) technology was applied in this study to measure sugar concentrations below 10%. The influences of temperature and species of sugars were evaluated. The results indicated that the TDR methods could be used for measuring sugar concentrations. The slope of TDR waveforms at a specific range was found to be a function of sugar concentrations and temperature. The differences in TDR waves derived from various sugar species and TDR probes were insignificant. The effects of the concentration and temperature on the slope of the TDR waveforms were established by regression analysis. The accuracy of the TDR method to measure sugar concentrations in new independent samples was within 0.365%. This technique is inexpensive, rapid, in-situ and suitable for online applications.