The growing size of the multiprocessor system increases its vulnerability to component failures. It is crucial to locate and to replace the faulty processors to maintain a system's high reliability. The fault diagnosis is the process of identifying faulty processors in a system through testing. This paper shows that the largest connected component of the survival graph contains almost all remaining vertices in the (n, k)-arrangement graph A n,k when the number of moved faulty vertices is up to twice or three times the traditional connectivity. Based on this fault resiliency, we establishes that the conditional diagnosability of A n,k under the comparison model. We prove that for k ≥ 4, n ≥ k + 2, the conditional diagnosability of A n,k is (3k − 2)(n − k) − 3; the conditional diagnosability of A n,n−1 is 3n − 7 for n ≥ 5.