This instrument adopts the method of physics combined with chemistry, on the principle of Kjeldahl determination. It is consisted of two main devices, digestion device and distillation device. It adopts sealing and running water to operate. On the condition of no use of fuming cupboard, there is no environment pollution. It adds alkali automatically, distills continuously to get the effect of safe, correct, and rapid. This instrument is suitable for such industries like feedstuff, grain, foodstuff, brewery, and dairy to determine crude protein. It is also the ideal instrument for education in college.