MgB 2 thin films with superior superconducting properties are very promising for superconducting magnets, electronic devices and coated conductor electric power applications. A clear understanding of flux pinning mechanism in MgB 2 films could be a big aid in improving the performance of MgB 2 by the enhancement of J c . The fabrication advancement and the understanding of flux pinning mechanism of MgB 2 thin and thick films fabricated by using hybrid physical-chemical vapor deposition (HPCVD) are reviewed. The distinct kind of MgB 2 films, such as single-crystal like MgB 2 thin films, MgB 2 epitaxial columnar thick films, and a-axis-oriented MgB 2 films are included for flux pinning mechanism investigation. Various attempts made by researchers to improve further the flux pinning property and J c performance by means of doping in MgB 2 thin films by using HPCVD are also summarized.Keywords: MgB2 thin and thick films, HPCVD, flux pinning mechanism * Corresponding author: email: wnkang@skku.edu A review on the understanding and fabrication advancement of MgB2 thin and thick films by HPCVD CCs showed self-field J c values of the order of 10 7 A/cm 2 at 5 K as high as already obtained in MgB 2 thin films, however, J c decreases in response to an applied magnetic field [31,32]. Therefore, a complete understanding of the flux pinning mechanism could be a big aid in improving the performance of MgB 2 by the enhancement of J c , which is most important parameter in practical applications for an operation with low noise and lower power loss. The epitaxial MgB 2 thin films with uniform orientation of grains provide an ideal condition for investigating the vortex dynamics and flux pinning properties, in contrast to MgB 2 bulk system where grains are randomly orientated. In this article, we review the progress made in the last 14 years for the fabrication, understanding of flux pinning mechanism, and for improving the performance by doping in MgB 2 epitaxial thin and thick films by using HPCVD technique.