The theoretical predication of Kitaev spin liquid in honeycomb iridates triggered tremendous interests. We recently discovered a new candidate material, beta-Li2IrO3 with a 3D analogue of honeycomb lattice dubbed hyperhoneycomb lattice. beta-Li2IrO3 in fact undergoes a magnetic ordering below 40 K. Interestingly, by an application of pressure above 2 GPa, the magnetic order was suppressed and NMR measurements suggest a spin liquid state. We also observed a pressure-induced structural transition around 4 GPa at room temperature by x-ray diffraction, but the structure of high-pressure phase remains elusive. We propose to perform powder neutron diffraction experiment under pressure up to 7.5 GPa on PEARL in order to elucidate the key structural difference between the magnetically ordered and spin liquid states, and also to determine the crystal structure of high-pressure phase.