The power graph P(G) of a given finite group G is the simple undirected graph whose vertices are the elements of G, in which two distinct vertices are adjacent if and only if one of them can be obtained as an integral power of the other. The vertex connectivity κ(P(G)) of P(G) is the minimum number of vertices which need to be removed from G so that the induced subgraph of P(G) on the remaining vertices is disconnected or has only one vertex. For a positive integer n, let C n be the cyclic group of order n. Suppose that the prime power decomposition of n is given by n = p n 1 1 p n 2 2 · · · p nr r , where r ≥ 1, n 1 , n 2 , . . . , n r are positive integers and p 1 , p 2 , . . . , p r are prime numbers with p 1 < p 2 < · · · < p r . The vertex connectivity κ(P(C n )) of P(C n ) is known for r ≤ 3, see [22,9]. In this paper, for r ≥ 4, we give a new upper bound for κ(P(C n )) and determine κ(P(C n )) when n r ≥ 2. We also determine κ(P(C n )) when n is a product of distinct prime numbers.