A collimator and an inspection system having the collimator are disclosed. The collimator includes: a collimator body including a first part and a second part; a collimating slit formed between the first part and the second part and having a first end and a second end in a longitudinal direction thereof; and a shielding member which is movable relative to the collimator body such that both a beam divergent angle and an elevation angle of a ray beam propagating through the collimating slit are varied. An inspection system and an inspection method for scanning a vehicle are further disclosed.