Abstract: The conversion formula of zircon grade is relatively simple, but there are errors or simplifications in the conversion process of zircon grade in some geological and mineral exploration specifications and papers. This paper corrects the application errors in the conversion formula of zircon and other metal placer minerals. By demonstrating the two parameters in zircon grade conversion formula, comparing with the grade conversion formula of titanium placer with relatively deep research depth, and verifying in the grade conversion of sedimentary iron ore minerals, compare the error by convert the grade of ilmenite through Fe and TiO₂ elements, the general formula for grade conversion of metallic placer is finally determined based on the demonstration of grade conversion of zircon, ilmenite, rutile, perovskite, magnetite and hematite. The analogical and validated formula defines the significance of metal or metal oxide mass fraction in metal placer minerals and the important of representativeness of phase analysis sample, and increases the proportion of metal or metal oxide in the mineral form of metallic placer, such as the proportion of zircon form ZrO₂ in zircon grade conversion, improves the accuracy of mineral grade conversion of metal placer and ensures the effectiveness of reserves estimation in geological and mineral exploration.