The work aims to study the distribution and change law of the temperature field inside the incubator during its thermal insulation when the ctesms is placed at different positions. The fundamental model of incubator was established in the finite element method by ICEMCFD, and four kinds of layouts were built by changing the placement of the ctesms inside the model, including the side placement (two kinds), top placement and edge placement. The convective heat transfer of internal air and heat conduction of box were unified as a whole to carry out the thermal-fluid coupling analysis by Fluent. The general rule of temperature field distribution inside the incubator was obtained. With the different positions of the ctesms, temperature field distribution was very different when the edge placement was of the biggest difference, followed by the side placement. The temperature field of top placement was distributed the most uniformly. In terms of available volume, temperature field uniformity and average temperature inside the incubator, it is no doubt that the top placement is the best choice for the ctesms.