Thermal rectifier, which transports heat preferentially in one direction, plays a significant role in thermal circuits. An efficient thermal rectifier should exhibit great different thermal conductivity with the forward and reversed temperature gradient. Thus, the rectifying coefficient defined by the ratio of kf and kr. However, the majority of thermal rectifiers show low rectifying coefficient or have a rigorous temperature requirements. In this work, we show an efficient thermal rectifier in a temperature-sensitive hydrogel synthesized with melamine and 6,7-dimenthoxy-2,4[1H,3H]-quinazolinedione in molar ratio 1:1 at 303K. DSC and rheology results indicate that a thermoreversible first order phase transition occurs when the temperature rises above its upper-critical-solution-temperature(UCST), which can be owned to H-bonding breakage suggested by the Raman-spectra. In this study, the suspended micro-device based on the differential bridge method is applied to measure the thermal conductivity of single hydrogel nanofiber picked out from the dispersion. The thermal conductivity of hydrogel nanofiber reveals an abrupt change with the phase changes. This study provides an efficient realization of a thermal rectifier for heat management that could be implemented in moderate temperature with high rectifying coefficient.