In this paper, we propose a simple max-min power control scheme for Multi-User MIMO (MU-MIMO) in massive MIMO systems. We model and formulate the issue as a max-min fairness power control problem, which needs to be considered in order to provide good experienced service for users in the system. By exploiting the special properties of the solution, we are able to propose a very simple power control algorithm with complexity O(M(N+M)) where M and N are the number of users and base station antennas respectively. In addition, only the estimated channel response and maximum transmit power of each user are required as input information. We implement the proposed algorithm on a record-playback massive MIMO testbed to verify the performance in real environment. The result show that the received signal quality of the worst user is much more improved, and all users experience roughly the same level of quality of service. In addition, simulation is carried out to confirm the advantage of the proposed scheme in term of minimum spectral efficiency.