For a class of nonlinear systems, a new adaptive predefined time sliding mode control (SMC) method is proposed in this brief. Based on the definition of predefined time stability (PTS), a new theorem of PTS is proposed, which introduces an exponential term to accelerate the convergence speed of the system. The introduction of adjustable parameters makes the design of the controller more flexible. And on the basis of the proposed theorem, this brief further presents a theorem of practice PTS, which enables the algorithm of PTS to be combined with other advanced algorithms. This brief combines the proposed theorem with adaptive SMC. Finally, the simulation results show the proposed control method has better control performance.