The invention provides an integration method of a vertical nanowire device of an air side wall structure. In the method, through hole etching and epitaxial channel material integration are combined, and an upper active area air side wall structure is manufactured. Compared to a traditional silicon dioxide or silicon nitride side wall structure, in the structure of the invention, a relative dielectric constant of air is 1 so that a stray capacitance between a grid electrode and an upper active area can be greatly reduced; the upper active area is taken as a drain terminal of the device, and a stray capacitance of the drain terminal is optimized so that a frequency characteristic of the device can be greatly improved. Simultaneously, a lower active extension area is heavily doped and is taken as a source terminal of the device so that a source terminal resistance can be reduced and degeneration of a device on state current is decreased. Light doping of one side of the channel in an upper active extension area is transited into heavy doping of one side of the upper active area so that penetration of a drain terminal electric field to a channel area can be reduced and simultaneously a low drain terminal resistance is maintained. The method is compatible with a traditional integration circuit manufacturing technology. The technology is simple and cost is low.