Alkaline pretreatment of lignocellulosic biomass produced certain amounts of alkaline-soluble lignin and phenolic compounds in the hydrolyzate, which might bring a negative effect on the alkali reuse for continuous biomass pretreatment. In the present work, lignin recovery from the alkaline rice straw hydrolyzate by ceramic ultrafiltration was investigated in terms of lignin retention and fouling mechanisms. Results showed that over 75% of lignin was retained using a ceramic membrane with the molecular weight cutoff (MWCO) of 5000 Da. The relative higher cross-flow velocity and lower pressure led to less resistance and membrane fouling, and complete or intermediate pore blocking was the most possible fouling mechanism. The alkaline solution from an ultrafiltration permeate was recycled for the pretreatment of fresh rice straw after a simple pH adjustment. By comparing the composition of solid residues and its enzymatic hydrolyzate after pretreatments with fresh and recycled alkaline solutions, it was found that the alkaline hydrolyzate could be polished by ultrafiltration for further reuse (at least four cycles). Moreover, the alkali recycling from the hydrolyzate could retard the release of phenolic compounds during the pretreatment. The consumptions of NaOH and water were reduced by 42% and 50%, respectively, during pretreatments with reuse of alkali. Alkali recycling benefits lignocellulose biorefinery by decreasing the costs associated with water and alkali supplementation as well as wastewater treatment.