The following suggestions are made on the health standards of working environment in railway tunnels under construction in China, on basis of investigations and analysis on the standards of gases in railway tunnels in China and foreign countries: first, the types of the occupational exposure limits should be identical with those specified in China's national standards and should meet the requirements of the relevant international standards; secondly, loose international values should be adopted for the occupational exposure limits and the occupational exposure limits for carbon monoxide should be different between high altitude areas and nonhigh altitude areas; thirdly, the tunnels should be divided into sections, for which different health standards should be adopted.