The right internal quality control rules are really important for improving the quality of patient results report in clinical laboratory.In order to look for faster and simpler tools that will help laboratories select the right internal quality con-trol rules for their own applications,recently Westgard introduced a newer tool “Westgard Sigma Rules”which is quicker and easier to use than previous tools.And it is very easy to figure out the right internal quality control rules by using West-gard Sigma Rules.This article introduced the characteristics and usage of original Westgard Rules and sigma metrics graph, and focusing on the application methods and practices of Westgard Sigma Rules which is the combination of original West-gard Rules and sigma metrics graph.Once the sigma quality of the tests and methods in laboratories are calculated,the West-gard Sigma Rules diagram can make it easy to select the right control rules and the right number of control measurements.