This paper considers resource allocation in distributed massive MIMO (DM-MIMO) system for enhanced mobile broadband (eMBB) and ultra-reliable low-latency communication (URLLC) slices. By maximizing average throughput of the system subject to quality of service (QoS) and slice isolation constraints, we formulate a mixed-integer optimization problem, which is non-convex and then converted to a convex problem by big-M formulation, integer relaxation and difference of convex (DC) programming. The penalized successive convex approximation (SCA) algorithm is proposed to determine the optimal resource allocation scheme. Simulation results show that the proposed scheme significantly improves average throughput of cell edge users and efficiently manages resource allocation in eMBB and URLLC slices.