Reptiles are ectotherms whose body temperature is impacted by ambient temperatures. We selected the toad-headed lizard (Phrynocephalus przewalskii) as our research objects and collected their activity body temperatures, ground temperatures and air temperatures in the field from September 28 to October 5, 2005 (Table 1). Statistical analysis showed that there was no significant difference in activity body temperatures between ages and genders. Lizards began to be active when the ambient temperature was higher than 20 ℃, and the body temperature of lizards increased gradually with time from 8:40 to 12:00 (Fig. 1). However, after 12:00 pm, the body temperature of lizards was lower than the ground temperature and remained at a high level (Fig. 1). The body temperature of lizards during the activity period was significantly correlated with the ground temperature and air temperature (Fig. 2). Lizards could quickly adjust their body temperature to a higher level in a short period and at a low ambient temperature, which is of great ecological significance to ensure their sufficient predation time, effective escape from natural enemies as well as efficient digestion.