NOVELTY - Comprehensive utilization of lignocellulosic biomass, comprises performing N grade acid hydrolysis on lignocellulosic biomass by adding freshly prepared acid solution into a first grade acid hydrolysis reactor, adding acid solution into second stage acid hydrolysis reactor, then into third stage acid hydrolysis reactor, discharging acid solution as final pentose solution, removing out acid hydrolysis residues, loading fresh lignocellulosic biomass raw material, treating the acid hydrolysis residues by using an alkaline solution to extract alkaline lignin; and performing enzymatic hydrolysis.    USE - The method is useful for comprehensive utilization of lignocellulosic biomass (claimed).    ADVANTAGE - The method achieves maximum resource utilization of lignocellulosic biomass.    DETAILED DESCRIPTION - Comprehensive utilization of lignocellulosic biomass, comprises (a) performing N grade acid hydrolysis on lignocellulosic biomass by connecting N grade acid hydrolysis reactors end to end, where one of the reactor is designed as a first stage and finally set reactor is designed as N stage, adding freshly prepared acid solution into a first grade acid hydrolysis reactor, adding the acid solution discharged from first grade acid hydrolysis reactor into a second stage acid hydrolysis reactor, adding the acid solution discharged from second grade acid hydrolysis reactor into a third stage acid hydrolysis reactor, following the process in the order until the N-1 grade acid hydrolysis reactor, finally adding the acid solution discharged from N-1 grade acid hydrolysis reactor into a N-stage acid hydrolysis reactor, discharging acid solution from N-stage acid hydrolysis reactor as final pentose solution, removing out acid hydrolysis residues from the first stage acid hydrolysis reactor, then loading fresh lignocellulosic biomass raw material, taking the first stage acid hydrolysis reactor as N-stage acid hydrolysis reactor, the second stage acid hydrolysis reactor as the first stage acid hydrolysis reactor, the third stage acid hydrolysis reactor as the second stage acid hydrolysis reactor, and the N-stage acid hydrolysis reactor as N-1 grade acid hydrolysis reactor, performing hydrolysis reaction to achieve continuous hydrolysis of lignocellulosic biomass, where the temperature of first stage acid hydrolysis is 100-150 degrees C, subsequent hydrolysis reaction temperature is reduced by 5-25 degrees C, and N is greater than or equal to 2; (b) treating the acid hydrolysis residues by using an alkaline solution to extract alkaline lignin; and (c) performing enzymatic hydrolysis on the alkaline hydrolysis residues obtained by alkaline hydrolysis treatment in the step (b) by using cellulase to obtain a solution with glucose as a main component.