The critical behavior of the antiferromagnetic interaction spin-1 system model in an external magnetic field is studied by using the constant-coupling approximation for four different nearest-neighbors coupling constant. First, we have investigated the thermal variations of the sublattice magnetizations for different values of the interaction parameters in an external magnetic field. The model exhibits distinct critical region, including the first-order, the second-order tricritical point, and the zero critical point region. Second, we have calculated the phase diagrams. Finally, a discussion and a comparison of the phase diagrams are given.