Polyaniline (PANI) doped with p-toluene sulfonic acid (PTSA) was synthesized by chemical oxidation method under the condition of conventional magnetic stirring (PTSA-PANI) and ultrasonic vibration (uPTSA-PANI) separately. Acrylic resin elastomer (ArE) was synthesized via radical polymerization. Novel all-organic dielectric elastomer composites (refer to the resultant composites herein as ArE/PTSA-PANI and ArE/uPTSA-PANI) were obtained by solution casting method. Chemical and microstructure characterization of the two kinds of resultant composites suggested that uPTSA-PANI possessed larger crystalline domain than that of PTSA-PANI and a unique branched structure. The dielectric properties of composites were measured in a wide frequency range, and the results demonstrated that both ArE/2.0% PTSA-PANI and ArE/2.0% uPTSA-PANI owned a high dielectric constant of more than 30 at 100 Hz, representing ten times increase with respect to neat ArE matrix (ae 3). Moreover, it was found that ArE/2.0%uPTSA-PANI held better comprehensive dielectric properties at high frequency than that of ArE/2.0% PTSA-PANI composite; that was to say, ArE/2.0% uPTSA-PANI composite possessed not only high dielectric constant but also low dielectric loss. In addition, the thermogravimetric analysis indicated that the composite possessed better thermal stability than that of neat ArE. In addition, the elastic modulus of ArE/2.0% uPTSA-PANI composite was lower than 5 MPa.