To obtain a silicone fluid having a high refractive index by hydrosilylating an arylacetylene with a linear or cyclic hydrogensiloxane.

An arylacetylene (e.g. phenylacetylene or diphenylacetylene) and a linear or cyclic hydrogensiloxane are reacted with each other in the presence of a catalytically effective amount of a platinum group metal to obtain a silicone fluid having a viscosity (at 25°C) of 100-40,000cP and a refractive index of 1.5 or above. In an actual example, a mixture comprising 85.45g of phenylacetylene, 12.36g of 1-hexene, 70.74g of a poly(methyl hydrogen) siloxane terminated with trimethylsiloxy units and having 10 methylhydrogensiloxy units on the average and a platinum catalyst is heated at 60°C for 1hr under agitation and then heated at 75°C for 2hr. The hexene is removed by distillation to obtain 162g of a transparent orange liquid having a refractive index of 1.5465.