The invention relates to a fixing device for a rat oral and nasal inhalation exposure experiment, which comprises rat fixators, a multi-layered support (6) for the rat fixators, a supporting plate (9), an exposure chamber (7) and exposure chamber connecting openings (8), and is characterized in that the multi-layered support (6) is arranged on the supporting plate (9) and surrounds the exposure chamber (7); brackets (4) of the rat fixators are fixed to the corresponding positions of the multi-layered support (6); the front end of each rat fixator provided with a faeces and urine collector (3) is steadily connected with the corresponding exposure chamber connecting opening (8), the main body of the rat fixator is arranged on the correspondingly mounted bracket (4), and the rat fixator is firmly fixed by an elastic fixing belt (5) arranged on the bracket (4); and the rat fixators, the multi-layered support (6) for the rat fixators and the exposure chamber connecting openings (8) are in steady corporation. The fixing device can ensure that the rat fixators are firm and reliable in the experiment process, and even if experiment rats struggle, the condition that the rat fixators are loose cannot happen.