The distribution characteristics of infrared images of liquid-layers in etching process of semiconductor are studied. Through the processing of infrared images, characterization of thermal convection between liquid-layers at any time is realized. The chemical reaction occurred in the etching process of semiconductor can result in energy release and absorption which can cause the exchange of energy between liquid-layers, and hence lead to the change of etching temperature. This characteristic can be monitored by an infrared thermal imager in real time and thus the basis can be laid for the further analysis and characterization of thermal convection of liquid-layers. Experimental results have shown that the closer the location to the interface of semiconductor material with the etching liquid, the more remarkable the temperature change of liquid-layers is. Moreover, the temperature is decreased in a gradient form from internal area to external area around the semiconductor material. The thermal convection of horizontal liquid-layer is obviously quicker than that of the vertical liquid layer. The extracted infrared cross-section image can clearly characterize the temperature changing characteristics of the horizontal liquid-layer and the vertical liquid layer. The method is of important value to the analysis of thermal convection information of liquid-layers at any time.