In this correspondence, an uplink nonorthogonal multiple access (NOMA) system where the base station (BS) trends to decode the independent information of users occupying the same radio resource simultaneously is considered. Different from the traditional successive interference cancellation (SIC) decoding scheme where the later decoding can only be processed after the successful decoding of the previous users, an advanced SIC decoding strategy is proposed to achieve outage balancing for the later decoded users. Under the proposed SIC decoding mechanism, the BS regards the unsuccessfully decoded users information as the interference on the following users, i.e., even the outage occurs for any of the previous decoded users, the BS will still try to decode the following users information. The outage performance with the new decoding strategy is theoretically analyzed. The closed-form expressions of the outage probability for each user are derived for an uplink 2-user NOMA system. The accuracy of the theoretical results is verified by the simulations.