Abstract: Described here in the essay is an inner diameter limit gauge suitable for steel pipes with different sizes, involving the R & D background, and focusing on main aspects of the gauge such as the technical features, operation method, and issues that need to be taken care during on-the-site operation.The said limit gauge as developed features wide applicable scope, accurate judgement and satisfactory safety performance, being able to multiply enhance the inspection efficiency.Compared with the similar gauge as previously employed, using the said limit gauge will get the acquisition cost reduced by at least 60%.