To address the safe tracking problem of systems caused by the conflict between desired trajectory and sudden changes of actual output constraints, an adaptive safe tracking control strategy is proposed in this paper for a class of uncertain nonlinear systems with unknown control direction, unmodeled dynamics and time delay. A secure boundary protection method(SBPM) is proposed based on a new prescribed finite-time performance function(PFTPF). The SBPM can automatically construct two adaptively adjusted secure boundaries to ensure that the system satisfies both the secure boundary constraints and the control performance specified by PFTPF. In this method, a bidirectional filtering smoothing mechanism(BFSM) is proposed, which significantly suppresses the large jitter of the control input.