We demonstrate the necessary and sufficient criterion for an N qubit Greenberger-Horne-Zeilinger (GHZ) state in white noise when it is divided into N−j parties with N≥2j+1 for arbitrary N and j. The criterion covers more than a half of all the separabilities of N-qubit Greenberger-Horne-Zeilinger states in white noise. For the rest of multipartite separable problems, we present a method to obtain the sufficient conditions of separability using linear programming.