The invention provides a separation and comprehensive utilization method of all components of crop straw. The separation and comprehensive utilization method of all the components of the crop straw comprises the steps of cooking crushed crop straw under the catalytic action of diluted hydrochloric acid by means of organic acid liquid, then conducting solid-liquid separation to obtain filter liquor, namely A liquid, washing filter residues with water until the filter residues are neutral, and then conducting drying to obtain crude cellulose; after the crude cellulose is treated by hydrogen peroxide, conducting solid-liquid separation to obtain filter liquor, namely B liquid, washing filter residues with water until the filter residues are neutral, and then conducting drying to obtain cellulose; conducting reduced pressure distillation on the A liquid and the B liquid separately, mixing obtained distilled products, after a pH is adjusted, conducting solid-liquid separation to obtain filter liquor, namely C liquid, washing sediment with water until the sediment is neutral, and then conducting drying to obtain lignin; adjusting a pH of the C liquid, then adding industrial alcohol, and then conducting solid-liquid separation; and washing sediment with water until the sediment is neutral, and then conducting drying to obtain hemicellulose. By means of the separation and comprehensive utilization method of all the components of the crop straw, the three components of the cellulose, the hemicellulose and the lignin in the straw can be successfully separated, and the recovery rates of the three components are high, so that comprehensive utilization of the straw is truly achieved.