The utility model relates to a reactor of a multistage fixed catalyst bed, which mainly solves the problem of poor catalyst hydrogenation effect in the prior art. The problem of poor catalyst hydrogenation effect is better solved by adopting the following technical scheme: the reactor comprises a reactor body (1), a liquid guide cylinder (5) and a liquid tray (6), wherein the liquid guide cylinder (5) comprises a guide cylinder wall (14), an upper opening and a lower opening (16); a catalyst supporting plate (11) is arranged at the bottom of the upper catalyst bed of the two adjacent catalyst beds and comprises a supporting plate outer edge (12) and a vertical hole (13); the liquid tray (6) comprises an upper extended tray side wall (17) and a tray side wall upper edge (18); the lower opening (16) of the guide cylinder is arranged in the liquid tray (6), and the tray side wall upper edge (18) is higher than the lower opening (16) of the liquid guide cylinder (5). The technical scheme can be applied in the industrial manufacturing of the reactor of the multistage fixed catalyst bed.