The invention relates to a hydraulic pressure supply control device used for hydraulic fracturing experiments, and an experiment method thereof. The hydraulic pressure supply control device comprises a diaphragm pump, a booster pump, and a water diversion steel cushion; the inlet end of the diaphragm pump is communicated with a water source pipeline; the outlet end of the diaphragm pump is communicated with a outlet end pipeline of the booster pump, and another outlet of the outlet end of the booster pump is communicated with a water diversion channel pipeline of the water diversion steel cushion via a high pressure pipeline; the water diversion steel cushion is detachably arranged on the surface of a test piece in a press machine; the booster pump is used for delivering high pressure liquid obtained via pressure increasing into the test piece via a water diversion channel. Operation of the hydraulic pressure supply control device is simple; continuous, stable, and accurate providing and recording of water pressure can be realized in a large pressure range. In hydraulic fracturing experiments, the hydraulic pressure supply control device can be connected with a single-shaft, a double-shaft, or a three-shaft press machine for test piece hydraulic fracturing; equipment connection and operation are simple; water pressure supply is stable; pressure value can be automatically controlled; detailed recording of pressure value and pressure change is realized; and experiment effect is excellent.