The invention provides a power distribution box with an adjustable top cover and a good heat dissipation effect. The power distribution box comprises a power distribution box body which is provided with a box door; the top of the power distribution box body is provided with a frame and a top cover is arranged at the top of the frame; the center of the top of the top cover is provided with a groove; a solar cell panel is arranged in the groove; the top cover is inside provided with a cavity in which an accumulator is installed; one side of the accumulator is provided with a circuit main board which is provided with a single-chip microcomputer; a fan is installed in the power distribution box body; a discharge pipe is installed at the top of the fan and one side of the fan is provided with an intake pipe; the intake pipe is inside provided with a filter screen; the inner wall of one side of the power distribution box body is provided with a temperature sensor; two sides of the power distribution box body are provided with first fixing plates; the top of each fixing plate is provided with a first electric push rod. The power distribution box has the advantages of compact structure, good heat dissipation effect and long service life.