We have investigated surface morphology and visible light emission from slow ions Kr15+, 17+ colliding with GaAs (100). The surface disorder of GaAs films mainly depends on the charge state of incident ions. The two spectral lines of target atom Ga belong to transitions of GaⅠ 4p 2P1/2o5s 2S1/2 at 403.2 nm and 4p 2P3/2o5s 2S1/2 at 417.0 nm. Light emissions of target species depend on the energy of the incident ions deposited on the target surface atoms. During the neutralization process, the four spectral lines of Kr+ respectively can be attributed to the transitions of Kr Ⅱ 4d 4F7/25p 2D5/2o at 410.0 nm, 5s 2P3/25p 4S3/2o at 430.4 nm, 5p 4D3/2o4d 2D3/2 at 434.0 nm and Kr Ⅱ 4d 4D1/25p 2S1/2o at 486.0 nm. They are induced by cascade de-excitation after many electrons of the conductions band of the solid surface captured in highly excited states of the incident ion. Intensities of these six spectral lines from incident ions Kr17+ are obviously larger than Kr15+'s.