Bio-oil is a promising alternative energy source to crude oil for broad application prospects. Bio-oil can help us avoid over-reliance on petroleum resources and significantly reduce pollutants and greenhouse gas emissions, improve environment conditions, and protect ecological systems. However, bio-oil applications have been impeded because of limited technologies, and poor bio-oil quality has posed a great challenge. As such, considerable research efforts have been made for realizing its potential application value. Scientific and technical advancements on methods of bio-oil quality improvement to date are reviewed, with an emphasis on advantages and disadvantages of each method. It also points out barriers and gives some recommendations to enhance bio-oil combustion performance in the future. Copyright (C) 2017 John Wiley & Sons, Ltd.