A method and a system for controlling a reverse link rate by using the number of active users who are carrying out communication in a CDMA 1xEV-DO mobile communication system is disclosed. A value of rise-over-thermal (ROT) at each antenna end of a wireless base station is measured and compared with a threshold ROT which defines an allowable limit of the ROT. A reverse activation control bit is set as 0 if the measured ROT value is smaller than or equal to the threshold ROT. The number of the active users is compared with a threshold user number which defines an allowable limit of the active users if the measured ROT value is greater than the threshold ROT. The reverse activation control bit is set as 0 if the number of the active users is smaller than or equal to the threshold user number. The reverse activation control bit is set as 1 if the number of the active users is greater than the threshold user number.