The oxygen free SiC fiber (Hi-Nicalon) has been commercially produced by an electron beam curing process. And then the SiC fiber (Hi-Nicalon Type S) having stoichiometric SiC composition and high crystallinity has been developed. Hi-Nicalon fiber has higher elastic modulus and thermal stability than Nicalon fiber. The Type S fiber has the highest elastic modulus and thermal stability and excellent creep resistance in three types of Nicalon fibers. Recently，Type S fibers as industrial products have been developed and put on the market. The Type S fibers have a high tensile strength of 2.8 GPa, a high elastic modulus of 390 GPa. Against thermal exposure, Type S retains a tensile strength of 2.3 GPa and hardly changes its elastic modulus even at 1873K. Moreover, Type S has outstanding creep resistance. Type S shows higher stress relaxation ratio than many other ceramic fibers after thermal exposure over 1673K. Now, Hi-Nicalon Type S fiber/BN/SiC composites are being developed as the components of gas turbine for aerospace and land based power generation such as shrouds and combustors. Type Hi-Nicalon S can be supplied about 30 kg per a month at present.