The invention relates to a device and a method for measuring the porosity and the grain breakage rate of compressed piled sand. The device mainly adopts a theory of communicating vessels and micro-compressibility of water and comprises a hydraulic device, a sealing rubber base block, a compression base block, an internal metal mold, an internal transparent observation window, an external glass measuring tool, bottom communicating micro-channels and the like; fine sand as a proppant is added to the internal metal mold, then water is added to the mold until the piled sand is just submerged in the water, the piled sand is compressed through the compression base block, the water subjected to compression flows into the external glass measuring tool through the bottom communicating micro-channels, and the increased water yield, namely, the reduction degree of the porosity of the piled sand can be read. The device and the method have the beneficial effects as follows: the porosity change and the grain breakage rate of the compressed piled sand as well as the proppant embedding degree can be measured, and support is provided for optimization of a proppant laying manner and prediction of the relation of sand packed crack width with pressure change; the device is simple in structure, light and easy to operate.