Optical guidings in Ramarn FELs are studied theoretically and calculated. We have performed a two-dimensional program （FELOG）

which is used to study optical guidings without and with wave-guide constructions. The numerical simulatins include optical field profile optical field radius. filling factor

and equivalent index of refraction

etc. The simualated results from experimental parameters agree well with experimental results. And the factors that affect optical guidings are analysed and discussed.