According to thermodynamics, solid state reactions will generally proceed to their 100% completion once they start; however, they may stop at the equilibrium state in case that there is a solid solution with continuously changing concentration. Solid state reactions also have the following characteristics:(1) they could produce stereoselective products;(2) the particle size of the products could be very small(nano-sized);(3) there is the lowest temperature for the reaction to be initiated. Here, it is particularly pointed out that a little solvent can be employed to accelerate solid state reactions with consequent safety and effectivity, but not the equilibrium; also, the solvent can make the solid mixture more fluidized, thus the mass transportation can be speeded up by a proper blender. In addition, solid state reactions can be used to assemble materials step by step, since any complex reactions can be decomposed to a series of reactions of two reactants. Consequently, studies on solid state reactions can lead to greener chemical processes. All those are demonstrated in this paper with solid state coordination reactions, which are the reactions of solid inorganic metal compounds and solid organic or inorganic ligands. The solid state coordination reactions are well known that they take place at near room temperature up to 300 ℃ without the help of solvents, just like the solid state organic reactions.