The invention discloses a power electrical transformer with a good heat dissipation effect, which comprises a box body, a cover plate is arranged at the top of the box body, the box body is fixedly connected with the cover plate through screws, heat exchange assemblies are arranged on the front surface and one side of the box body, heat insulation cavities are formed in the side wall and the bottom wall of the box body, and the multiple heat insulation cavities are communicated with each other. A transformer functional assembly is arranged in the box body. The heat insulation cavity is filled with cooling oil to isolate external heat, the air circulation performance in the box body is high, multiple heat dissipation modes are matched, a reasonable heat dissipation mode is autonomously selected for operation by using an adjusting system according to the real-time temperature and requirements, the heat dissipation efficiency can be maximized, the heat exchange corrugated plates distributed in a snake-shaped stacking mode are combined with the oil passing holes, the superficial area of the heat exchange face is greatly increased, cooling oil is combined for cooling, the heat dissipation efficiency is greatly improved, the device is convenient to install and connect, and the heat exchange assembly can be conveniently detached, cleaned and maintained.