Given a hypergraph H(V;E), a set of vertices S in V is a vertex cover if every edge has at least a vertex in S. The vertex cover number is the minimum cardinality of a vertex cover, denoted by t(H). In this paper, we prove that for every 3 uniform connected hypergraph H(V;E), t(H)<=(2m+1)/3 holds on where m is the number of edges. Furthermore, the equality holds on if and only if H(V;E) is a hypertree with perfect matching.