The invention provides a method for preparing pentaerythritol as well as manganese formate and sodium chloride. The method comprises the following steps: the waste liquor generated during the production of pentaerythritol through the condensation of formaldehyde and acetaldehyde is distilled under reduced pressure to obtain a saturated solution of pentaerythritol, and then the saturated solution of pentaerythritol is cooled to obtain pentaerythritol crystals and a filtrate I after filtering separation; the filtrate I is distilled under reduced pressure to obtain saturated solution of sodium formate, and then the saturated solution of sodium formate is cooled to obtain sodium formate crystals and a filtrate II after filtering separation; the pentaerythritol crystals are washed, dried and crushed to obtain pentaerythritol; the sodium formate crystals are dissolved in water to react with manganese chloride solution to obtain solution containing manganese formate and sodium chloride, and then the solution is filtered to obtain few filter cake impurities and a clear filtrate III; and the filtrate III is distilled, cooled and crystallized to obtain a mixed product of manganese formate and sodium chloride.