This paper makes study of pulping process for rice straw in basic ionic liquid [NH-(C2H4OH)3]+. The pulp yields increases with extended time, which the concentration of residual lignin in rice straw pulp gradually declines. The results indicate that the temperature 100℃ and time 60min are suitable for cooking pulping. Separated lignin is scanned by IR and fiber analysis. Triethanolamine ionic liquid [NH-(C2H4OH)3]+ can well dissolve lignin which contains large number of hydroxyl groups. The lignin with lilacs and guaiac structures has the better dissolving performance at 100℃. It is known that fiber length is 0.758mm, width 22.8μm by detecting its size. The pulp fibers are mainly fine ones, which are in line with straw pulp characteristics.