Abstract: This paper mainly does the experimental research about transition to chaos of thermocapillary convection in the rectangular pool. In the experiment, we observed that the transition process of thermocapillary convection in the rectangular pool has different phases of steady, regular oscillation and irregular oscillation. For different Prandtl numbers of silicone oil in different aspect ratios, there are different transition routes to chaos. When Prandtl number of silicone oil is less than or equal to 16 (1cSt) or Prandtl number equal to 25 (1.5cSt) with aspect ratios of 26, thermocapillary convection transition follows quasi-periodic bifurcation routes to chaos as the temperature increases. But when silicone oil of Prandtl number is greater than or equal to 25, it mainly follows period-doubling bifurcation routes to chaos. Sometimes two types of bifurcation would be accompanied by emergence of tangent bifurcation. In the experiment, we observed the distribution of the temperature field of liquid surface by using thermal imaging cameras, and found some phenomena of the surface fluctuation and convective cell oscillation.