[en] In order to optimize the chemical composition of developmental Ni-Cr-W superalloy for VHTR applications, the influence of Cr/W ratio on corrosion behavior was studied. The test materials have various Cr/W ratio systematically and also contain 1 wt% Mn and 0.3 wt% Si to improve the corrosion resistance in simulated VHTR helium. The corrosion tests were carried out in simulated VHTR helium under the thermal cycling between R.T. and 900, 950 and 1000degC up to 1000 h. The results obtained are summarized as follows, (1) The weight gain of specimens and the spallation of surface oxide film were less on the alloys with low Cr contents (high W contents). The alloys contained Cr below 20 wt% showed the good oxidation resistance. (2) The thickness of surface film and the depth of internal oxidation decreased with decreasing the Cr content of the alloys. (3) At 900degC and 950degC all alloys were carburized. The decarburization was observed in the alloys with Cr content below 20 wt% at 1000degC. (4) The heat treatments for the soild solution or grain boundary precipitated not influence on the corrosion behaviors. (5) The surface films were consisted of two layers which were the outer MnCr₂O₄ spinel oxide layer and the inner Cr₂O₃ oxide layer. The oxidation resistance of the alloys were improved by the addition of Mn. (author)