As the largest land mammal that ever lived on the earth, giant rhinos have received much attention from researchers around the world. Here, we use linear models based on limb bone length and circumference measurements of many living animals to estimate the body mass of giant rhinos, with the help of a new composite skeleton of the giant rhino (Dzungariotherium sp.) from the Qingshuiying Formation, Lingwu, northern China. Our estimate suggests that Dzungariotherium sp. from Lingwu is one of the largest giant rhinos known, with a body mass of 20,558 kg. Under the limitation of materials, we estimated the body mass of giant rhinos in as many species as possible by different methods. The body masses of other giant rhinos are also estimated with adjustments based on the new composite skeleton. The data obtained on Dzungariotherium have been considered together with other data on giant rhinos to observe the evolutionary tendency of the group at a large geological scale. It shows that giant rhinos experienced a rapid body size increase since the Late Eocene and divided into three stages, coinciding with the global temperature falling and the spread of the open environment.