As part of a new approach to convert biomass to liquid fuels, we investigated the effects of alkali treatment on the property and performance of HZSM-5 catalyst for oligomerization of biomass-derived ethylene under atmospheric pressure. The characterization results showed that alkali treatment led to an increase in the total and mesopore volumes but a decrease in the surface area and micropore volume. When NaOH concentration was low (<0.5 M), the ZSM-5 structure was largely preserved with the increase in the mesopores and acidity, while higher NaOH concentration can severely destroy the zeolite structure, resulting in a significant reduction in the micropores and acidity. The ethylene oligomerization results showed that not only the ethylene conversion and the liquid yield increased but also the catalyst stability was improved after proper NaOH treatment. The relationship between the structure and performance has then been discussed.