The invention discloses a mounting method for a waste heat boiler. The mounting method comprises specific steps as follows: parameters of low-frequency noises in noises produced by the waste heat boiler are acquired, and the wavelength lambda of the low-frequency noises is determined according to the acquired parameters of the low-frequency noises; when the waste heat boiler is mounted, the distance between the waste heat boiler and a wall is larger than the result obtained after lambda is divided by 4, and lambda is the wavelength of the low-frequency noises; the low-frequency noises are at the frequency ranging from 16 Hz to 20 Hz. According to the characteristic of low frequency of the horizontal type waste heat boiler, the distance between the waste heat boiler and the wall is larger than the result obtained after lambda is divided by 4 when the waste heat boiler is mounted, so that all of or most of the low-frequency noises pass through the wall and are transmitted to the outside, and absorption of the low-frequency noises is facilitated.