A method of preparing monopentaerythritol, dipentaerthritol, and sodium formate through high temperature condensation and cascade recrystallization is disclosed. The method lowers the energy consumption dramatically and improves the cost-effectiveness by carrying out the reaction in a non-low-temperature zone, and thereby avoiding the requirement for refrigeration. The method alleviates the difficulty of separation and improves the product quality by means of cascade separation process, and thereby avoiding the low purity from a single separation. In addition, the mother liquor obtained after each separation step is recycled to the previous step as the recycling liquor, which avoids discharging waste, increases the product yield and lowers raw materials consumption.