In DS‐CDMA systems with the successive interference cancellation (SIC) technique, there are K! possible decoding orders for K active users and the decoding order has considerable impact on system performance. Once the constraints on the received powers of mobile stations and the bit‐energy‐to‐interference‐power‐spectral‐density ratio requirements are satisfied under some decoding order of SIC, the system is feasible. Otherwise, if the constraints are violated under all possible decoding orders, the system is infeasible. It is highly time‐consuming to examine the system feasibility directly by using the usual exhaustive search method (ESM) for a system with even moderate number of users. In this paper, we propose an efficient approach for examining the feasibility of DS‐CDMA systems with imperfect SIC. The proposed approach has significantly lower computational complexity than that of ESM and thus benefits the quick decisions of admission control and/or scheduling, which are essential for Quality of Service provisioning in DS‐CDMA systems. Furthermore, we theoretically prove that the system under the resultant decoding order obtained by the proposed approach is able to achieve the lowest outage probability among all possible decoding orders. We conduct extensive simulation experiments, and the numerical results validate our analysis and demonstrate the effectiveness of our approach. Copyright © 2010 John Wiley & Sons, Ltd.