In this paper, we consider the covert communication design assisted by a multi-antenna jammer. A multi-antenna transmitter (Alice) sends information to multiple single-antenna users (Bob) simultaneously while avoiding detection of a warden (Willie). We first establish the signal transmission model in multi-user system and the detection model of Willie. Then, we focus on joint beamforming design of transmitter and jammer. Under the conditions of covert constraint, received signal-to-interference-plus-noise ratio (SINR) constraint, and transmit power constraint, the objective is to maximize the system’s covert capacity, i.e., the sum of the receiving rates of multiple users. To solve this optimization problem, we transform it into a solvable convex form through semi-definite relaxation (SDR) and quadratic transformation, and design an iterative algorithm accordingly. Finally, numerical results are provided to verify the effectiveness of the proposed beamforming design.