Feedstock properties are an important factor affecting the process yields and economics of fast-pyrolysis biorefineries. This study develops a fast-pyrolysis process model sensitive to feedstock properties based on experimental results. Sixty-four simulations are run to evaluate the impacts of carbon, ash, and moisture content in biomass feedstocks on process yields and energy consumptions. An economic analysis is conducted for each run to quantify process economics under different feedstock properties. With biomass feedstocks of 48% carbon and 15% moisture, minimum fuel selling price (MFSP) increases from $0.97/L to $1.06/L when ash content increases from 1% to 7%, due to reduced hydrocarbon yields. With biomass feedstocks of 48% carbon and 3% ash content, MFSP increases from $1.03/L to $1.08/L when feedstock moisture increases from 15% to 45% as a consequence of increased energy demand for feedstock drying. The impact of feedstock ash content decreases gradually as ash content increases. Feedstock carbon content has less significant impacts on process economics in this study.