Abstract: Speaking of oil casing thread gauges, more and more home-made products are being substituted for the foreign-made ones. However, up to now, for tracing the size of measurement of this category of gauges, no fully-established specification is available. The paper describes a newly-invented patented product, i.e., the multi-functional master gauge for casing thread gauges, covering such aspects as the development background, details of the invention, structural characteristics and operation procedure, etc.