This invention discloses an olefin oxidation process, including a step of under olefin oxidation conditions, successively passing a reaction feed from the No.1 catalyst bed through the No.n catalyst bed, wherein if the apparent velocity of each of the reaction materials passing from the No.1 catalyst bed through the No.n catalyst bed is respectively named as v 1 to v n , and if m represents any integer in the region [2, n], the relationship v m-1 m holds. The process according to this invention is capable of extending the service life of the catalyst, especially the single-pass service life thereof, and at the same time, suppressing any side-reaction over a prolonged period of time. This invention further discloses a fixed-bed reaction apparatus and a system for olefin oxidation.