In this paper, we study the global existence and nonexistence of solutions to the following semilinear parabolic system {u(t) - Delta u = v(p) in M-n x (0, infinity), v(t) - Delta v = u(p) in M-n x (0, infinity), u(x, 0) = u(0)(x) in M-n, v(x, 0) = v(0)(x) in M-n, where M-n (n >= 3) is a non-compact complete Riemannian manifold, Delta is the Laplace-Beltrami operator. We assume that both u(0)(x) and v(0)(x) are nonnegative, smooth and bounded functions, constants p, q >= 1. (C) 2009 Elsevier Ltd. All rights reserved.