Purpose Gadolinium-based MRI contrast agent media has been widely used for decades.This contrast agent can dramatically improve the sensitivity and specificity in many pathology tissues.Although there are alternative choices available,gadoliniumbased contrast agents are still dominant.This abstract aimed to review from the fundamental theory to the clinical application of gadolinium based contrast agent.Methods The reason why gadolinium can be effective as a MRI contrast agent is that it has 7 unpaired electrons and is thus paramagnetic.It can shorten the T1 and T2 relaxation time of the nearby photons.However,gadolinium is a heavy metal and is toxic in biological system so it has to be chelated with other molecular.Nowadays,there are many different forms of gadolinium chelation complexes available for clinical uses.They differ from their basic chemical structures to metabolism pathway.All these differences will affect our choice in proper usage for specify tumor or patient.Results Although gadolinium based contrast agent has been used safely for million people,its safety is still a concern.Nephrogenic systemic fibrosis associated with gadolinium based contrast agent has been reported since 2006.Also,latest study revealed that gadolinium may remain in brain after injection.This phenomenal raised concerns and study about long term effect is still warranted.Conclusion Gadolinium based contrast agent is valuable for patients and has been used for decades.It is believed to be safe if we use it with proper guidelines.Although latest study raised some problems that we cannot ignore,based on the benefit from contrast agent we get,we can only continue what we did before until we find any new findings.