We have proposed to determine the ion temperature from the heat flux data obtained with the thermal probe. In this paper, we made a prototype of the thermal probe and tested it with the glow discharge plasma. In order to use thermal probe in high temperature plasma, rapid measurement method without bias voltage scanning is preferable. Using the sheath particle/heat flux formula, well-known triple probe method is expanded to include the ion heat flux measurement. It is shown that there exists the possibility to measure ion temperature directly. (c) 2005 Elsevier B.V. All rights reserved.