A boiling heat transfer test unit was designed and built. The TH5104 infrared thermography was used to measure the wall temperature of a microtube to research the characteristics of boiling heat transfer of refrigerant in the microtube. The test piece was a single stainless circular tube with an external diameter of 1.22 mm, an internal diameter of 0.86 mm and a length of 200 mm. The infrared photography was used to test and record the wall temperature of the microtube with heat flux ranging from 65 kW/m2 to 231 kW/m2 at different mass fluxes from 1 726 kg/m2·s to 8 635 kg/m2·s. Experimental results indicate that the wall temperature distribution along the axial direction has a regular change obviously. For the flow boiling in the horizontal microtube, a large temperature difference along the whole tube is shown during the evaporation of fluid in the microtube. Whether the difference of wall temperature is positive or negative,it is relative to the heat flux. The variation of the wall temperature is affected by the heat flux, flow patterns of working fluid and the heat transfer model,and the more complex the flow pattern is, the more severe the wall temperature varies.