Zhejiang Univ, Dept Phys, Hangzhou 310027, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
We consider a gauge model based on SU(3)(L) x U(1)(x) symmetry. In the model each lepton family contains a new neutral fermion (N-particle). We calculate the lifetime of the N-particle and estimate the value of its mass. We show that the N-particle can act as dark matter particle.