The combination of orbital angular momentum (OAM) and massive multiple-input multiple-output (MIMO) brings the possibility of almost infinite transmission capability, which may be applied in the coming 5th generation networks and beyond. In this study, a uniform line array (ULA)-based massive OAM-MIMO scheme in a multipath scene is presented. The cumulative phase of OAM carriers and multiple reference coordinate systems relative to each transmitting antenna are used to describe the OAM-MIMO wireless channel model theoretically. The performance indices of interest including capacity, energy efficiency, and capacity gain are numerically investigated in detail. The results indicate that the presented ULA-based massive OAM-MIMO scheme performs better overall than a conventional MIMO scheme via enhancing the OAM multiplexing intensity, and multi-fold capacity gain can be obtained especially in the low signal-to-noise rate communications.