Due to great demands on solid rocket motor and solid ramjet for thrust control, the experimental study on the effect of high voltage electric fields on the combustion characteristics of solid fuel polymethyl methacrylate （PMMA） nwascarried out. The effect of electric fields on the flame structure of PMMA, as well as its burn rate, temperature and flame flow-field was analyzed. The results show that the deformation of PMMA flame is significant under the negative electric fields. When larger electric fields are imposed, their effects on the flame become more significant. The high-voltage electric fields can greatly change the burn rate of PMMA. The burn rate of PMMA increases with the applied positive voltage amplitude by about 34.2%. Under the negative electric fields, the burn rate of PMMA decreases firstly with the increase of the voltage amplitude, and then increases. The burn rate can be decreased by about 15.7%, and it can also be increased by about 15.4%. The maximum temperature of PMMA is decreased when it is subject to the electric fields. The PMMA flame flow increases with the amplitude increase of the voltage. The interaction of buoyancy and electric volume force may be the factors that lead to the change of flame shape, temperature and the thermal feedback of the flame to the solid phase.