The invention herein discloses a method and its equipment for fast and complete dissolution and hydrolysis of lignocellulosic biomass. Lignocellulosic biomass is placed in a dilute alkaline solution and then rapidly heated to a temperature between 329˜367° C. to achieve complete dissolution of the lignocellulosic biomass as biomass solution in 0.7˜2 s. The biomass solution is further hydrolyzed rapidly to hydrolysates at homogeneous conditions. The solubilized biomass solution is easy to rapidly hydrolyze into sugars to produce bio-fuels and other value-added products, and to rapidly quench to produce micron particles in the continuous flow equipment at high pressures and high temperatures. The invention herein provides a simple and low-cost method to quickly dissolve and hydrolyze biomass with great potential for a novel biorefinery.