The present invention relates to a photoactive compound of a novel structure represented by Chemical Formula 1 below In Chemical Formula 1, R1 and R2, R3, and A are as defined in the specification, and a photosensitive resin composition comprising the same. The photoactive compound of the present invention comprises a nitro group and a phosphonate structure and thus exhibits excellent sensitivity through efficient absorption for UV light, excellent compatibility between the photoactive compound and the alkali-soluble binder resin, and an improved solubility of the photosensitive resin composition. Furthermore, the photosensitive resin composition of the present invention has excellent residual film thickness and mechanical strength characteristics and heat-resistant, chemical-resistant, and development-resistant properties. Accordingly, the photosensitive resin composition of the present invention is advantageous in hardening the column spacers of liquid crystal displays, an overcoat, and passivation materials and also advantageous in a high-temperature process characteristic.