Mouthing core which is used for ensuring dimensional precision of formed mouthing cavity in the cast pipe is subjected to the impaction of high temperature Fe melt and enormous centrifugal forces during centrifugal pouring process.Technological index and structural characteristics of sand core were described.The identification and merits and dismerits of hand-made core-making conventional boxcore base and modified boxcore base with large aperture were analyzed.The practical production verifies that modified boxcore base can greatly decrease the failure rate of boxcore and improve appearance and formation rate of sand core as well as decreasing labor intensity and reducing energy consumption.