The utility model discloses a fixed fluidized bed reactor in oil processing field, which solves the problems of poor repetitiveness of test data and uneasy and inaccurate control of stock oil temperature in the prior art. The utility model is mainly characterized in that the stock oil and steam inlet path is formed by an oil inlet pipe (6) and an outer tube (7) sleeved around the outer wall of the oil inlet pipe (6), a steam inlet passage (17) is formed between the oil inlet pipe (6) and the outer tube (7), an atomization nozzle (11) is provided at the bottom of the oil inlet pipe (6) and the outer tube (7), at least two layers of partitions (10) are provided axially inside a reaction section (16), reaction oil-gas delivery tubes (8) and filters (9) are paired at a number of three, and a plunger valve (13) and a catalyst discharge tube (12) are provided on a shell (1) at the bottom of the reaction section (16). The utility model is used for the performance evaluation of catalytic cracking catalyst and the characteristic analysis of stock oil.