DTD serial desolventizer is one of the best equipments of desolventizing in extraction oil plant, and it can finish desolventizing, cooking and drying the extracted meal. Cooperated with steam drying conveyor designed by our company, it can adjust the outlet temperature of meal to meal to 5-10℃ above surrounding temperature and the meal can be packed and stored directly. Pre-desolventizing adopts four-story indirect steam heating, desolventizing adopts direct steam heating and drying adopts hot air. In each story, there is stirring and auto-control equipment, thus making pre-desolventizing, desolventizing and drying completely, and decreasing the residual solvent in the meal effectively. On the basis of keeping the protein activity in the meal on the utmost, the activity of urease is decreased to about 0.3mgN/g.min(30℃).