As the current bioconversion of lignocellulose mainly towards on bioenergy, a bioproduct with higher value would be promising to improve the profit output from the process. Straw lignocellulose, hydrothermally pretreated by ammonium sulfite, was used as the substrate to produce high-value microalgal biomass in this study. Medium based on the lignocellulose hydrolysate were prepared to cultivate four locally isolated microalgal strains, Chlorella and Scenedesmus species. All of the microalgal strains well adapted to the lignocellulose hydrolysate. Among the strains, C. ZTY4 had the highest growth rate in hydrolysate-based medium with a generation time of only 10.2 h, which was much shorter than that in glucose medium (16.7 h) and former reports. The polyunsaturated fatty acids (PUFA) content of C. ZTY4 reached to 66.4% in total fatty acids of C. ZTY4, which was well qualified for high-value applications. C. ZTY4 was identified as Chlorella pyrenoidosa by 18S rDNA sequencing. This research proposed a bioconversion approach from straw lignocellulose to high-value microalgal biomass and screened C. ZTY4 as a qualified strain.