Due to the increasing power requirements of the electronic components, which in many cases leads directly to increasing production of heat flux is the topic of the electronic cooling still current. In order to maintain their quality and lifetime as long as possible is the heat dissipation of electronic components solves by sophisticated technology such as a heat pipe technology. The paper deals with the cooling of power electronic component by loop thermosiphon. The loop thermosiphon is one from many proposal of heat pipe devices. Object of the paper is design and construction of the device to provide heat removal from the electronic component, thermal visualization of loop thermosiphon during operation, evaluation its cooling efficiency and research results interpretation. Paper describes function principle of loop thermosiphon, testing of the loop thermosiphon function and measurement of cooling efficiency in dependence on input electric power of the electronic component. The findings from measurement of loop thermosiphon cooling efficiency are compared with natural convective alumina cooler on the end of paper. The main object of the work is thermal visualization of heat flux transport by working fluid in loop thermosiphon from evaporator to condenser evolution. The result of the thermal visualization loop thermosiphon give us how the hydrodynamic and thermal processes which take place inside affect overall heat transport at start-up and during loop thermosiphon operation and distribution dynamics of the working fluid in dependence heat load.