Boron-doped diamond thin films are homoepitaxially grown on 3 mm×3 mm×1 mm commercial Ib(100) diamond substrate with high temperature and high pressure(HPHT) by microwave plasma chemical vapor deposition(MPCVD). The magnetron sputtering and electron beam evaporation techniques are used to prepare the diamond Schottky diodes with different structural parameters. The test results indicate that the surface of the growed diamond thin films are very smooth and obvious atomic steps can be observed. The device has obvious rectifier features. The forward conduction resistance of the device is 20 Ω at 300 K when the diameter of Schottky electrode is 100 μm, the distance between the Schottky electrode and ohm electrode is 10 μm and the applied voltage is -15 V. The reverse saturation current is about 10-6 A and the reverse breakdown voltage is about 103.5 V. The greater the distance between the Schottky electrodes and ohm electrode is, the higher the reverse breakdown voltage is and the smaller the forward current is.