A novel alkali-soluble hyperbranched photosensitive polysiloxane urethane acrylate (AHBPSUA) was synthesized by using hyperbranched polyesters, hydroxyl-terminated polysiloxane, dimethylolpropionic acid, isophorone diisocyanate, and 2-hydroxyethyl acrylate as raw materials, and its structure was characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, and H-1 nuclear magnetic resonance spectroscopy. It was found that AHBPSUA possessed good compatibility with a number of acrylate monomers. The effect of photoinitiators and monomers on the photopolymerization kinetics of AHBPSUA was investigated by real-time infrared spectroscopy (RT-IR). The results showed that AHBPSUA could rapidly photopolymerize under UV irradiation in the presence of a photoinitiator and the optimal concentration of the photoinitiator (Darocur 1173) was determined as 0.1 wt %. The resin of AHBPSUA with common acrylic monomers exhibited a high polymerization rate and double-bond conversion and could form a regular image under UV irradiation through a patterned mask. The AHBPSUA system could dissolve in 1 wt % sodium carbonate solution easily and completely, and the cured coating film of the AHBPSUA system possessed excellent flexibility, toughness, and heat resistance.