Introducing biomass-derived additives into microalgae cultivation to increase its yield has been regarded as a more cost-effective and environment-friendly method compared with gene-editing and nutrients supplementation. In this research, feasibility of three major phenolic compounds from lignin’s basic structures (guaiacyl-, hydroxyphenyl- and syringyl- types) for freshwater microalga Euglena gracilis cultivation was evaluated. The results indicated that trans-4-hydroxy-3-methoxycinnamic acid (HMA), 4-hydroxybenzaldehyde (HBA), and syringaldehyde (SRA) could all promote microalgae growth in a phytohormone-like role, and the highest promotion effect was achieved under HMA treatment. HMA at 0.5 g·L−1 enhanced the cell biomass yield by 2.30 times, while HBA and SRA at the concentration of 0.1 g·L−1 increased the yield by 1.30 and 1.21 times, respectively. In addition, increased carotenoids and lipid biosynthesis were also observed under the treatments of phenolic compounds, which would contribute to the microalgae biofuel production, since the growth and lipid accumulation of E. gracilis were simultaneously enhanced.