This paper aims to determine the thermal conductivity for two types of functionalized carbon nanotubes (FCNT “Taunit M”) nanofluids. FCNT1 and FCNT2 have been used to enhance the thermal conductivity of nanofluids. Six concentrations of 0.01, 0.02, 0.03, 0.05, 0.07, 0.1 wt.% loading of FCNT1 and three concentrations of 0.01, 0.05, 0.1 wt.% loading of FCNT2 have been used in this experiment. The experiments were achieved at temperatures 40°C. The technique for measuring thermal conductivity was described and manufactured at Tambov State Technical University. As a result of the study, the effect of increasing concentrations of FCNTs in the aqueous medium on thermal conductivity was presented. The relationship was nonlinear in FCNT1. The maximum enhancement thermal conductivity was 11.6 and 7.1% loading FCNT1 and FCNT2 respectively, which achieved at a weight fraction of 0.05 and 0.1 % respectively. Finally, the latest researches in this field were presented for comparison in the results obtained.