Abstract: The developed red clay exists in Dalian district. Through being compared with limestone and clay in chemical composition, the reasons why some elements of the red clay run off or collect are analyzed. In order to reveal its peculiar physical characteristics, the water invade test and the soil body shrink test on the red clay are respectively carried out in aboriginal and air-dried state. Through the test resuts, some phenomena of the red clay are explained, such as the irrecoverability of this red clay disintegrated by water, and the stability of earth body excaved at natural moisture condition.