The poor scientific literacy of Chinese farmers is an important factor in restricting social development of China, which Chinese government has realized. Therefore, Chinese government begins to attach importance to the research on farmers’ scientific literacy. As the basis of subsequent research, how to exactly estimate the scientific literacy of Chinese farmers is the first consideration. The current assessment on scientific literacy of Chinese farmers has such disadvantages as lacking of special assessment on scientific literacy for Chinese farmers, ignorance of heterogeneity of farmers, results’ scientificity being lowered by the methods of assessment and the overall assessment being affected by design on single vision.This paper points out that constructing a scientific and reasonable index system of scientific literacy for Chinese farmers should abide by the following 5 principles: scientificity, pertinence, comprehensiveness, stability and keeping pace with the times. Based on defining connotation and extension of scientific literacy of Chinese farmers, this paper discusses and constructs the estimating index system on scientific literacy of Chinese farmers.