In this study, we synthesized 1,1,1-trimethlyolpropane (TMP)-based diol which has a pendant anionic group and a reactive double bond in the pendant cyclic ring. Then, a water-based urethane acrylate crosslinking agent (CA) was prepared from isophrone diisocyanate (IPDI), 2-hydroxyethyl acrylate (2-HEA), and a low molecular weight diol bearing pendant carboxylic acid. The CA content was varied in order to investigate the influence of the added content on the mechanical and dynamic mechanical properties. The diol used in this study was TMP-cis-1,2,3,6-tetrahydrophthalic anhydride (TPA) which was synthesized from the esterification reaction of TMP with TPA. This diol was liquid at room temperature. As the CA increased, the initial modulus and elongation at break decreased. Also, increase of the rubbery plateau modulus was observed by dynamic mechanical analysis (DMA). This result was believed to result from an increase in the crosslinking density in the mixtures. Shift of the T-gh to a higher temperature was also observed by DMA. This is due to the increased hard segments and the phase separation.