The present invention relates to a mobile communication system, and more particularly, to a method of adjusting a signal power in a variable data rate mode. Accordingly, the present invention includes steps of allocating a reference pilot signal level to each of a plurality of data rates supported by the system and adjusting the reference pilot signal level for a changed data rate based on an external control information and adjusting a power control threshold for secondly adjusting the reference pilot signal level corresponding to the reference pilot signal level.