The present invention belongs to the technical field of medicinal preparation. The invention discloses a formula of a neostigmine bromide slow release preparation which can be taken once every day for treating myasthemia gravis, functional flatulence after being performed an operation and urinary retention, as well as its preparation method. The preparation is disclosed as a slow release tablet form composed of a skeleton core containing neostigmine bromide and the slow release preparation and a coating. The neostigmine bromide slow release preparation of the present invention is capable of overcoming the disadvantage of present medicament common tablets in the market, slowly releasing to keep stable blood and medicine concentration, acting for a longer period, possessing low toxicity andside effect and conveniently taking the preparation, and the slow release preparation keeps effective blood and medicine concentration for a long time, reduces the medicine taking frequency, raises the compliance of the patients and reduces the side-effect due to over peak concentration. The invention has the advantages of simple preparation technology, low cost, easy control and easy industrial production.