The strong light absorbing Cu<sub>2</sub>ZnSnS<sub>4</sub> (CZTS) nanocrystals are interesting material in photovoltaic applications owing to the abundance and non-toxicity of the material. The optoelectronic property of CZTS light absorber depends on the size of nanocrystals which confines the electronic states within it. In the complex colloidal medium it is very difficult to predict the size of the particles by only theoretical calculations. However, suitable chemical approach is able to tune the size of the particles by adjusting the chemical potential of the medium for different sizes of CZTS nanocrystal formation. Here, we reported the size control of CZTS nanocrystals which were made by a hot-injection method using organic ligands based colloidal medium. The influence of solvent systems, within following five pure and mixing solvent systems: Oleylamine, 1-Octadecene + TOPO, mixture of Oleylamine:Oleicacid (1:1,v/v%), Oleicacid + TOPO and Oleylamine:Oleicacid (1:1,v/v%) + TOPO , and composition of metal precursors were studied. The final CZTS nanoparticles showed wurtzite crystal structures, and size of the particles can be tuned through different combination ratio of metal precursors. Our results indicate that metal precursor composition ratio has a pivotal role to tune the optoelectronic properties of CZTS nanocrystals for the photovoltaic applications.