Abstract: An ion funnel interface for ion transmission at high pressure (0.5~1 torr) has been built and implemented in a quadrupole vacuum chamber. The performance of the ion funnel was compared to a traditional capillary/skimmer ion transmission interface by ion current measurements. The ion funnel interface consists of 28 ring electrodes with gradually decreasing inner diameters, and was operated under an optimal DC gradient, RF frequency and RF amplitude. Ion transmission efficiency for selected biomolecules such as YGGFLR, insulin chain B, ubiquitin and cytochrome c in different sample concentration approaches 90%. The ion funnel interface can efficiently transfer analyte ions at high concentration up to 100uM with a factor of 3-7 better ion transmission compared to that with a traditional capillary/skimmer interface, based on the ion current measurement at the entrance of the hexapole ion guide at a lower pressure chamber (10-2 torr). Coupling of the ion funnel with surface induced dissociation mass spectrometry may allow the study of ion internal energy distribution in the ion funnel.