A novel control barrier function-based discrete-time adaptive control is presented for uncertain safety-critical systems, which can ensure the asymptotic convergence of tracking error while guaranteeing the estimation parameter within a safety set. Firstly, a discrete-time adaptive law is proposed with the control barrier function (CBF) to ensure the safety of estimated parameters based on the forward invariance of sets. Then, a discrete-time adaptive control architecture is synthesized, and its Lyapunov stability analysis is proved by a logarithmic Lyapunov function. Last, numerical example is provided to illustrate the convincingness of the proposed method.