On the basis of literature [7], the unreliable buffer zone is introduced into the unreliable dual-equipment production line system, and the system state probability change is analyzed on the basis of the discrete model. Using the literature [7] research method, the form of the internal state probability of the system is guessed, and the internal state equation is substituted to obtain the solution satisfying the internal state equation. If the conjecture is correct, then one must find a linear combination of this set of solutions satisfying the boundary conditions. By processing the probability of the relevant states of the system equipment and buffer, the solving order of the problem is reduced, and an approximate analytical method for evaluating the performance of the system is discussed and developed, and the research algorithm is given. Simulation results show the effectiveness of the proposed method.