The content of crude fiber (CF) in feed is an important index to evaluate the nutritional value of feed. The traditional method of measuring CF is cumbersome, the accuracy of the measurement results is low, and it is not suitable for the analysis of batch samples. This article takes the measurement of crude fiber as an example to illustrate the operation process of the automatic fiber analyzer, summarizes the details that need to be paid attention to during the experiment and the skills of daily maintenance of the instrument, discusses and the effect of the experiment. The result shows that the automatic fiber analyzer using the filter bag technology to measure CF content is an internationally recognized measurement method, which has the advantages of high automation and high measurement accuracy.