Ultrasound spray pyrolysis system was used to obtain the Al doped ZnO nanocrystals. Aqueous solutions of zinc acetate (C4H6O4Zn-xH2O) was used as Zn precursors, and aluminum nitrate (Al(NO3)3) was used as Al precursors. All the used solutions were 0.2M. The Al/Zn atomic ratio in the solution was 0%, 1%, 3% and 5%. ZnO nanocrystals (NCs) deposited by ultrasonic spray pyrolysis at 450°C on the Si substrates have been investigated.Scanning electronic microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD) and photoluminescence (PL) methods have been used for the comparative investigation of ZnO and ZnO:AL NC films. All NCs are characterized by wurtzite crystal lattice, but the size of NCs change in dependence on Al contents. The SEM image of undoped ZnO NCs represents hexagonal grains with the size of 200 nm. The NC size decreases dramatically with rising the Al content in the films. PL spectra of all studied samples were studied at room temperature, as well as in the temperature range 10-300K. PL spectra were complex and onclude the near band edge (NBE) and defect-related emission bands. The Impact of Al doping on the emission and structural parameters has been discussed.