In pharmaceutical industry it is Found that 40% Of Active pharmaceutical Ingredients are poorly water soluble. So, oral delivery of such drugs is complicated because of their low bio-availability .solubility is one of the most important for orally administer drug to achieve desired concentration of drug in systemic circulation for more pharmacological action. For enhancement of solubility there is use a self microemusifying drug delivery system of lipophilic drugs. Mainly class II & IV drugs are follows the SMEDDS. this SMEDDS is prepared by combination of drug, oil, surfactant & co-surfactant/co-solvents . SMEDD system as like example diclofenac sodium to improve the rate extend of absorption such from GI tract .this formulation is evaluated by performing various tests such like as, thermodynamic stability, droplet size analyser ,liquefaction time ,refractive index, self-emulsifying time drug content study etc. This SMEDD formulation shows faster solubility &dissolution rate than plane drug .when solubility increases then absorption increases also bio-availability increases then shows the maximum therapeutic response. This review provides an updated in advancement in SMEDDS with regard to its components ,characteristics ,various tests & also various pharmaceutical significant.