It is well known that liquid ammonia is effective to improve the hand of cotton fabric and the treatment is carried out practically at present. In this study, we have done liquid ammonia treatment of regenerated cellulosefiber lyocell produced by the solvent spinning with N-methyl morphorine N-oxide. Change of the fiber structure by the treatment was investigated on the basis of the X-ray diffraction, dyeing properties, and KES shearing and bending hystereis characteristics. Cellulose II of the untreated lyocell was partially transformed to Cellulose III I I by the treatment and crystallinity decreased only a little compared with the untreated. Apparent dyeing rate, diffusion coefficent and saturation dye uptake were decreased a little by the treatment, while hand of the fabric was changed a little to stiffer. From these results, the NH 3 treatment of lyocell was not effective for improvement of the hand in comparing with the cotton fabric. Furthermore, polynosic fabric was treated with NH 3 and the effect was investingated with X-ray diffraction and dyeing rate.