Abstract: The review article introduce molecular imaging equipment small animal PET and PET-CT's philosophy and technique feature, small animal PET and PET-CT apply many new techniques and images resolution has obviously raising, as same time, small animal PET and small animal CT may come true image fusion, small animal PET and PET-CT permit us to engage molecular level imaging in vivo without invading, so small animal PET and PET-CT are good tool in medical molecular imaging.