A common packet channel assignment method and device in a CDMA (Code Division Multiple Access) communication system is disclosed. The method comprises transmitting an access preamble signal having channel information which is used to access a base station, and then receiving an; access preamble acquisition indicator signal from the base station in response to the access preamble signal. A collision detection preamble for detecting a collision is transmitted in response to the received access preamble acquisition indicator signal. A first signal indicating acquisition of the collision detection preamble and a second signal indicating channel assignment are received, both of which the base station has transmitted in response to the collision acquisition signal. Upon receipt of the first signal, a common packet channel is assigned according to information designated by the second signal.