The invention provides a process for preparing Guerbet alcohol. The process comprises the following steps: (a) weighing 100-200g of a fatty alcohol, a solid base catalyst and a nickel-based catalyst, adding into a three-necked flask which is provided with a thermometer, a water distributor, a reflux condensing tube, a nitrogen introducing tube and a magnet stirrer, introducing nitrogen into the three-necked flask continuously, increasing temperature to 200 DEG C rapidly, carrying out reaction for 1.5 hours, decreasing temperature after reaction, filtering a product of reaction at room temperature, separating the catalysts from the product of reaction, and distilling an obtained filtrate by reducing pressure to obtain a product, wherein the weight of the solid base catalyst is 5-15% of that of the fatty alcohol, and the weight of the nickel-based catalyst is 0.5-5.5% of that of the fatty alcohol; and (b) adding the product obtained in the step (a) and a nickel-based catalyst into a sealed reactor, replacing air in the reactor with nitrogen, controlling the pressure at 0.1-2.0MPa and the temperature at 120-280 DEG C with hydrogen, carrying out reaction under pressure for 1-3 hours, cooling a product of reaction to normal temperature, filtering to obtain a high-purity product, and measuring the iodine number, wherein the weight of the nickel-based catalyst is 1-5% of that of the product obtained in the step (a). The process provided by the invention has the advantages of strong operability, simple post-treatment process and significant improvement of product purity and is suitable for industrial production.