Abstract: The change trend of volatile fatty acid （VFA） in goat rumen after putting nylon bags with different kinds of forage was studied. The concentration of VFA in goat rumen after putting nylon bags with three kinds of forage was determined by using nylon bag method. The results were as follows： after the roughages with nylon bags were put in rumen, the concentration of acetate, propionate, butyrate, total volatile fatty acid （TVFA） concentration, and the ratio of acetate to propionate all firstly increased and then decreased,and reached the peak at four hours, among them the concentrations of acetate and propionate were 70.49% and 15.38%; the fermentation type of rumen totally leaned to acetate-propionate type; the three kinds of forage all contributed to feed goat. So the nylon bags with feedstuffs could affect the volatile VFA concentration, and it is in connection with the protein content of feedstuffs.