A semiconductor detector and a packaging method thereof. The semiconductor detector includes: a cathode circuit board including a read out chip, a high voltage side top layer of the cathode circuit board, a bottom connection layer of the cathode circuit board and a dielectric filled between the high voltage side top layer and the bottom connection layer, wherein the high voltage side top layer is connected to the bottom connection layer through a via hole; and a detector crystal including a crystal body, an anode and a cathode, the anode is connected to the read out chip of the cathode circuit board, the high voltage side top layer is connected to an input terminal of the semiconductor detector and the bottom connection layer directly contacts the cathode of the detector crystal to connect the cathode to the cathode circuit board.