Effect of cold working on erosion behavior in connection with recrystallization of Al-Mn alloy core brazing sheets was investigated. Cold rolled brazing sheets were heated up to predetermined temperatures. The microstructure was observed on the longitudinal section of the core and cladding alloys. The recrystallization temperature of highly cold worked specimens decreases with increasing cold working. On the contrary, the specimens cold rolled to 10-20% retain unrecrystallized structure having a high density of dislocation even at brazing temperature. The relation between the dislocation structure and erosion behavior during heating is also described. The completely recrystallized coarse grain of core alloy has shown an excellent erosion resistance.