The present application relates to a novel microalgae strain with the efficacy of promoting plant growth and a use thereof. When cultured in the presence of fermentation exhaust gas, a novel Chlorella vulgaris CD02-3002 strain according to an aspect grows fast with a high efficiency of photosynthesis and thus can effectively reduce the exhaust gas generated by microbial fermentation. Having the effect of promoting plant growth when applied to plants, a culture of the strain or a supernatant of the culture can be used as a fertilizer for plants and thus can be advantageously applied as a novel carbon reduction technique.