A mathematical model of droplet spreading on surface of an immiscible liquid based on lubrication approximation was used. Influence of viscosity ratio on evolution and equilibrium state of droplet at high viscosity ratios was investigated. Crucial parameters including droplet thickness and spreading radius were examined. It shows that deformation of the liquid-liquid interface near the contact line is affected by the viscosity ratio and the surface tension ratio; Increase of viscosity ratio reduces the spreading rate and the time constant, thereby, prolongs the spreading evolution. It does not affect the final stable shape of the droplet; Relation between spreading radius and time satisfies x_max= 1 - 0.2 exp(- βt). Inertial oscillation does not appear at the final stage of droplet spreading in the case of high viscosity ratios.