To accurately measure the surface temperature field of the microtube and solve the influence of axial heat conduction along wall of the microtube on convective heat transfer in the microtube, No-contacting temperature measuring method is firstly used in the microscale experiment. An experimental test loop, which can conduct some tests about micro-heat transfer and micro-flow for gas and liquid, is established. When distilled water is used as the working fluid and flowing through the microtube, a visual experiment about the surface temperature field is conducted, that is, the surface temperature field photos of microtube with inner diameter of 168µm and outer diameter of 406µm were acquired by employing the infrared thermoviewer and specially magnifying lens for the constant Re number and different heating powers. Further, the second order derivative about the temperature along axial microtube to the length is obtained. A simple mathematic model is set up and the correlation between the axially conductive heat and inner convective heat transfer is obtained by derivation. The experimental results and the theoretical analysis show that the quantity of axial heat conduction is considerable small and may be neglected compared to the convective heat transfer in the condition of single-phase.