A Piezo-hydraulic Energy Harvester (PHEH) was presented based on solid-fluid coupling vibration to harvest low-frequency and high-level vibration energy, and its structure as well as working principle were introduced. With an established energy-conversion model, the influence factors on the piezo-hydraulic harvester were analyzed. The theoretic results show that the output performance of the PHEH depends on the vibration frequency/level, the structure and size of piezodisc/cylinder, liquid volume/performance, and system backpressure. The desired performance can not be achieved unless the above parameters are matched well. By a piezodisc with a diameter of 60 mm and a thickness of 0.9 mm and a cylinder with a diameter of 16 cm and a length of 100 cm, a PHVI was fabricated and tested by taking water as liquid medium at different frequencies/backpressures/exciter-amplitudes. The test results suggest that there is an optimal vibration frequency (8 Hz) for the PHEH to achieve the maximal output voltage, which rises with the increasing of backpressure and vibration level. In the case of unvaried other parameters, the achieved voltage from the PHEH under 0.4 MPa is 1.65 times that under 0.2 MPa.