Various nanostructured CdS samples have been synthesized with assistance of starch (bio-polymer) by solvothermal method. We have synthesized nano-regime, nanorods and nanoparticles by simply changing the starch-solvent combinations. The highly polymeric (branched) structure of starch capped the CdS samples to modify the surfaces and hence tune the optical properties. The optical band gaps for three samples are 2.34, 2.37 and 2.38 eV. The photoluminescence emission peak also changes with surface modification of the nanomaterials. The sensitivity of the optical properties of CdS nanomaterials with structural modification by means of polymer may be used for practical application like solid state lighting.