To enhance the treatment effects of the atmospheric pressure plasma jet（APPJ） in the fields of material surface treatment

environmental protection

and disinfection sterilization

etc.

NH

3

/H

2

O were added to the Ar APPJ to improve the activity of the APPJ. The optical emission spectral intensities of NH

OH and O and the length of the plasma plume were investigated at various applied voltages and NH

3

/H

2

O ratios by optical emission spectra diagnosis and light-emission images

observation. The voltage-current waveforms and Lissajous figures were also recorded correspondingly. Results showed that the main species produced by APPJ in Ar/NH

3

/H

2

O included Ar

N

2

NH

OH

and O. As the applied voltage increased

the emission spectral intensities of NH

OH and O

the length of the plasma plume

discharge power and transported charges all increased. When the added NH

3

reached 0.012 5% in the Ar/NH

3

mixed gas

the emission spectral intensity of NH reached the maximum.

When H

2

O was added under this condition

it was found that the emission spectral intensities of OH and O reached the maximum values when the water vapor content was 0.25% and the emission spectral intensities of OH and O increased by 104.4% and 55.8% as compared with those of APPJ in Ar/NH

3

while the emission spectral intensity of NH decreased by 18.7%. The overall emission spectral intensities of the oxidizing particles（NH

OH and O） in Ar APPJ reached the maximum

and it should be more favorable for applications in materials hydrophilic modification and disinfection sterilization

etc.