An analytical model has been established to evaluate the thickness of the dissolution layer of base metal in a liquid brazing filler metal during a high temperature brazing process. The model was validated by a study of brazing of a TiAl alloy to a 42CrMo steel. Peak brazing temperatures were within a range of 1103-1203 K. The margin of deviation between predicted and experimentally determined dissolution thicknesses is within the range of 1-14 %, thus supporting the validity of the model well.