This study describes the effect of bifunctional reactive dyestuffs treatment on the fibrillation control and fine structure of lyocell fiber having different spinning conditions. Reactive dyeing process with bifunctional dyestuffs reduced the extent of fibrillation on the surface of fiver due to crosslinking of cellulose chain molecules by means of hydrogen bridges or covalent bondings. The crosslinking reaction was found to increase in the order of the coagulated fiber > washed fiber > dry and heat treatment fiber manufactured in the spinning process. The extent of the reduction of fibrillation was decreased with draw ratio. The decrease of fibrillation in case of using R-2G is lower than in case of using FN-2R. Therefore, the crosslinking reaction was found to be closely related with the diffusion of dyestuff, due to the fine structure of the fiber and the chemical structure of the dyestuff