The invention discloses a method of producing mono-pentaerythritol, dipentaerythritol and tri-pentaerythritol. The adopted production raw materials comprise acetaldehyde and formaldehyde. An activator adopts liquid alkali. The liquid alkali is sodium hydroxide or calcium oxide; neutralization reagent adopts formic acid solution; the acetaldehyde and the formaldehyde are both dived into a pre-condensation kettle which is pressurized with inert gases. Reaction liquid reacts for a period in the pre-condensation kettle, and then the reaction liquid is shifted to a main condensation kettle which is pressurized with the inert gases to keep on reacting. The alkalinity of the reaction liquids in both reaction kettles is maintained to be different. The concrete method comprises the following steps: materials preparation, charging pre-condensation, the diversion of the reaction liquid, constant temperature condensation, neutralization and separation, etc. By adopting the technology, the yield rate of the dipentaerythritol is enhanced to 45 percent from existing 21 percent, and the main conversion rate of the acetaldehyde is more than 90 percent.