The work aims to study the effect of ultrasonic pretreatment and humidity control on banana drying characteristics, in order to shorten drying time and reduce color deterioration of banana. First, the banana chips with a thickness of (5.0±0.1) mm were pretreated with single frequency (20, 40, 60 kHz) at a power of 300 W and a temperature of 30 ℃. Each frequency was divided into 3 groups with treatment time of 20, 30 and 40 min, and the optimal ultrasonic pretreatment time obtained was 30 min. Then, single frequency (20, 40, 60 kHz), double frequency ((20+40), (20+60), (40+60) kHz) and triple frequency ((20+40+60) kHz) were respectively treated, and the constant temperature hot air drying was carried out at 65 ℃. On this basis, hot air drying with drying media's relative humidity of 5%, 10% and 15% was carried out. In ultrasonic pretreatment, the ultrasonic pretreatment with single frequency (60 kHz), dual frequency ((40+60) kHz) and triple frequency ((20+40+60) kHz) had the best effect on the hot air drying rate under temperature and humidity control. Under the same relative humidity of dry medium, the order of drying rate, rehydration rate and Vc content from large to small in turn was triple frequency ((20+40+60) kHz), dual frequency ((40+60) kHz), single frequency (60 kHz) and blank control group. Under the same ultrasonic pretreatment conditions, the smaller the relative humidity of the drying medium, the higher the drying rate and the rehydration rate, and the lower the Vc content. The effects of drying media with different relative humidity on the drying characteristics of banana after ultrasonic pretreatment are explored to provide theoretical basis for selecting appropriate drying process.