The invention discloses a preparation method of a solar battery. The method comprises the following steps: texturing on the surface of a silicon chip; performing integrated diffusion on one surface of the silicon chip firstly to form a high surface concentration, a thick impurity glassy layer and a PN junction with a shallow junction depth, then performing laser propulsion to form a high-low-doped PN junction, and then depositing an antireflective passivation layer; and forming double-surface metal contact and obtaining the solar battery. The integrated diffusion comprises the following procedures: 1, performing low-temperature diffusion, depositing a certain impurity source on the surface, and then performing high-temperature propulsion; 2, performing low-temperature diffusion, and then performing low-temperature annealing; and 3, performing low-temperature diffusion. According to the preparation method of the solar battery, by use of an integrated diffusion technology, the uniformity of sheet resistance is improved, at the same time, a heavily-doped region with quite good uniformity can be obtained, an obviously-diffused high-low PN junction is formed on a diffusion surface, serial resistance is reduced, a filling factor is added, the shortwave spectrum response of the battery is improved, short-circuit currents and open-circuit voltages are improved, and the battery efficiency is improved.