This paper proposes a joint design of transmit beam-forming and reconfigurable intelligent surface (RIS) reflecting for radar sensing and single-user communications. The radar receiving signal-to-noise ratio (SNR) is employed as a performance metric of target estimation which we aim to maximize while guaranteeing a pre-defined SNR for the user communication. The obtained problem is non-convex, and we thus resort to alternating maximization as well as successive lower bound maximization methods to pursuit a stationary solution. Simulation results illustrate that with the aid of RIS, the proposed joint design indeed enhances radar detection performance. In particular, the radar receive SNR increases as the number of RIS elements increases.