The composition, structure, and colloidal stability of hydrocracked products at various hydrogen pressures were analyzed to investigate the role of hydrogen pressure in slurry-phase hydrocracking of Venezuela heavy oil. Experimental data showed that the formation of gas, naphtha, and coke was suppressed by a high hydrogen pressure during the slurry-phase hydrocracking. In addition, the maximum of light oil per coke ratio was observed at 8 MPa of hydrogen. The desulfurization and denitrogenation were promoted by the increase of hydrogen pressure. However, the influence of hydrogen pressure on the desulfurization rate was reduced at higher pressure, while the influence on the denitrogenation rate was still obvious. With the increase of hydrogen pressure, the Conradson carbon residue (CCR) of the vacuum residue (VR) product decreased. Meanwhile, the coking inducing period of the atmospheric residue (AR) product prolonged, which means that the colloidal stability of the AR product was enhanced by a high hydrogen pressure. Structural parameters of asphaltene were studied according to the reference of the Fourier transform infrared (FTIR) spectroscopy method of kerogen structure studying. The cracking and hydrogenation saturation of asphaltene were promoted by a high hydrogen pressure, which lead to the increase of the A factor (infrared absorption intensity ratio of saturated aliphatic carbon and aromatic carbon) and n(CH2)/n(CH3) of asphaltene products as well as the decrease of the Y factor (condensation index of asphaltene) and Z factor (discriminative index of the side-chain fracture situation of asphaltene).