Abstract The pulp black liquor accounts for about 90 percent of pollution of the whole paper and pulp industry. The clean production technology of extracting useful bio-based substances from pulp black liquor can increase wastewater utilization and benefit the environment. This paper examines chemical characteristics and biological activities of fulvic acid-like substance extracted from leonardite (FA1), which serves as the benchmark, and from pulp black liquor (FA2). Instrumental analyses with Fourier transform infrared (FT-IR) spectroscopy, 13C-nuclear magnetic resonance (13C-NMR) spectroscopy and 1H-nuclear magnetic resonance (1H-NMR) spectroscopy indicated that FA1 and FA2 shared common functional groups existed in typical fulvic acid. A series of rice seed germination bioassays proved that FA2 had the same growth promotion function as FA1. The optimal concentration for water absorption and seed germination was 5 mg/L for FA1 and 60 mg/L for FA2. FA1 and FA2 treatments also increased the activity of α-amylase under the action of hydrolytic enzymes and promoted root development by increasing cell size and cell division. The study implied that pulp black liquor can be used for bio-renewable and eco-friendly production of fulvic acid for wide applications in agriculture.