Stable structures of neutral, positive, and negative nitrogen-rich sulfides S(N-3)(m) (m = 1-4) were studied. Three minima of S(N-3)(2), one of S(N-3)(2)(2+), one of S(N-3)(3)(+) and one of S(N-3)(4) were optimized. An isomerization reaction pathway of SN3-, and dissociation reaction pathways of SN3- and SN3+ were investigated. The special properties of a sulfur atom, a large atomic radius and a loose electron density, allow the sulfur atom to link to several nitrogen atoms, and nitrogen-rich sulfides SNx (or ions) can be formed easily. The properties of high energy-density of S(N-3)(x) were investigated.