Abstract: It is well known that the patterns of dinosaur egg arrangement within the clutch differ from group to group (Young, 1965; Zhao, 1975, 1979; Zhao and Li, 1993). Some types such as elongatoolithid and hypsilophodontid eggs were laid regularly in nest. The long axis of these eggs forms certain angle with the ground (Plate I). But as for others, they were disorderly arranged in the nest. Zhao et al. (1994) advanced that dinosaur eggshells could be considered as rotational ' thin shell. When the dinosaur eggs were laid, and buried in sand for incubation, they were subjected to distributive pressure. Once the pressure comes to the critical value pcr , the eggshell will subside and then break. Here p cr is called the critical pressure of instability. It has been demonstrated that Variation between pcr of different kinds of dinosaur eggshells existed (Ma and Zhao, 1994). This suggests that arrangement patterns of dinosaur eggs in nests might have something to do with the eggshell ' s ability to resist external pressure. The purpose of this paper is to discuss the relationship between the pattern of egg arrangement in the nest and the critical pressure of its eggshell, and five types of dinosaur eggshells are available.