The water absorption and water retention properties of a mixture of pseudocarboxymethyl chitosan(a mixture of cellulose，hemicellulose and lignin substituted with 6-aminoacetic acid)obtained by sulfonation and calcium glycinate substitution with straw powder were evaluated.The research on its water absorption and water retention performance in outdoor soil shows that the mixture of pseudo-carboxymethyl chitosan is superior to the carboxymethyl chitosan products synthesized from natural chitosan raw materials in terms of moisture absorption rate and moisture retention rate；In particular，the 1∶1 compound of pseudo-carboxymethyl chitosan mixture and cellulose sulfate monoester has better moisture absorption effect，and its maximum saturated water absorption in soil is even better than that of polyacrylamide，reaching 35.5 g/g，and has the soil conditioning effect of significantly increasing soil water content，organic matter content，mechanically stable aggregate content，and reducing soil bulk density.The semi-synthesized pseudo-carboxymethyl chitosan mixture from straw has the advantages of easy availability of raw materials，simple production process，low production cost and excellent performance，and has great potential for development.