A series of urethane acrylate resins (UARs) having various amounts of hard segment were synthesized from poly(oxypropylene) diols (PPOs) with different molecular weights and characterized. The relationship between the morphologies and mechanical properties of these UAR (UARX-Y-Z, in which X means the molecular weight of PPO, Y means the content of hard segment, and Z means the content of comonomer) networks was investigated in detail. It was found that the morphology of the UARX-Y-Z network was related to the contents of hard segment and the comonomer (methyl methyacrylate-MMA) as well as the molecular weight of PPOs. The UAR1000-0-34 network synthesized from PP0210(M-n = 1000) is a homogeneous system due to the good compatibility between the PP0210 and the MMA segment. The UAR1000-0-60 network exhibits the morphology of partial microphase separation resulting from increasing the length of the MMA segment, so as to decrease the miscibility between the soft and hard segment. For the UAR1000-30-34 network having a higher content of the hard segment, the hard segments tend to form domains with the limited short-range and long-range order, leading to the formation of the microcrystallites, and therefore it shows higher tensile strength and elastic modulus. For UAR400-0-34 network with lower molecular weight PPO204 (M-n=400), a high glass transition temperature and some microcrystallites were observed. Such a network exhibits the best mechanical properties over all UAR networks studied.