The work aims to explore the thickness variation and drying characteristics of in-mold dried pulp molded products. The hot pressing drying experiments were carried out on three kinds of pulp molded products with different initial thickness by a pulp molding machine at different drying temperature. The thickness and quality change data of the products were analyzed, and the drying characteristic curve was drawn. The hot pressing drying process of molded pulp products could be divided into three processes:the pre-pressing stage, the constant speed drying stage, and deceleration drying stage. In the pre-pressing stage, the fluffy pulp molded wet blank was extruded and compacted by the mold, and the thickness value tended to be instantly thinned, with a thickness reduction rate of more than 40%. In the constant speed and deceleration phases, the thickness decreased gradually to an equilibrium value. According to the experimental results, the drying characteristics of molded pulp products based on thickness change are obtained.