In this paper, a novel type of micropore-rich boron nitride (BN) fibers (m-BNFs) was prepared by adding a surfactant hexamethylenetetramine in the traditional melamine-diborate (M.2B) precursor of conventional porous BN fibers (BNFs). As a result, extra micropore distribution could be introduced within m-BNFs bodies. Due to adding of the micropores, the CO2 capture capacities of the BN fibers were improved to be 2.85mmolg(-1), which were significantly higher than that of original porous BNFs. Also, these m-BNFs would have an enhanced adsorption capacity of methane, the amount of up to 0.71mmolg(-1). At the same time, these new m-BNFs materials showed excellent thermal stability, which would be more valuable for advanced gas adsorption working in a high-temperature environment in the future.