In order to identify the direct economic loss caused by sheep brucellosis in class I area of China and the financial rationality in its prevention and control，an index system of direct economic loss caused by the disease and a cost-benefit evaluation method of its prevention and control were established. A field visit and questionnaire investigation were conducted in 319 farms/households and the disease prevention departments in 17 cities/counties in 4 provinces which are the main sheep production area. 21 questionnaires from the disease prevention departments and 301 from farms/households were collected，covering 124 brucellosis infected farms and 177 brucellosis free farms. The questionnaire data were statistically analyzed by using Excel，SPSS and other software. The results showed that，in 2020，the average direct economic loss of each infected sheep was 4 557 yuan（excluding dairy sheep），and the loss in each province was from 0.18 to 2.04 billion yuan，especially in farms/households，accounting for 73.0%-81.0% of the total loss；the benefit-cost ratio of each government at province level for the disease control was about 5:1-38:1. It was concluded that serious economic loss was caused by the brucellosis which should be controlled to achieve significant economic benefits. Therefore，farmers and governments should increase their investment in the disease control，especially governments should improve their proportion of preventive inputs.