Understanding the relationship between structure and dielectric property of dielectric elastomers (DEs) is very important in their practical applications. In this work, we fabricated polyurethane elastomers (PUEs) with high dielectric properties using hydroxyl-terminated butadiene-acrylonitrile copolymer (HTBN) as soft segment and hexamethylene diisocyanate (HDI) and butanediol (BDO) as hard segment (HS). We also investigated the effect of HS content on the structure, mechanical, dielectric and electromechanical properties of HTBN-based PUEs. The HTBN-based PUEs were achieved larger than 8.7 of dielectric constant and lower than 0.02 of dissipation factor at 1 KHz. The dielectric constant and dissipation factor of PUEs were slightly decreased with increase of HS segment, whereas the breakdown strength and Young's modulus of PUEs were significantly increased. The actuated area strain of PUEs also showed decreased with increase of HS content under the same electric field. Our results indicated that the adjusting of HD structure via HS content is one of effective ways to optimize the dielectric and mechanical properties of PUEs. (C) 2017 Elsevier Ltd. All rights reserved.