The effect of grain size in nanocrystalline alloys is difficult to reveal experimentally because challenges of controlling a number of other microstructure factors. This paper designed and prepared a series of multilayered films with Al-TiB2 crystalline layers of different thickness but with amorphous layers of identical thickness. In these multilayered films, the heights of columnar crystals in crystalline layers were controlled from 8 to 128nm and their diameters kept at ~15 nm, independent of their heights. This design achieved the control of grain size, independent from other microstructure factors. The analysis of mechanical properties of these multilayered films showed that the inverse Hall-Petch phenomenon also exists in Al-TiB2 nanocrystalline alloys , as nanorystalline pure Al. The critical grain sizes of deviation from the Hall-Petch relationship and the inverse Hall-Petch phenomenon are approximately 32 nm and 8 nm respectively. These critical grain sizes are similar to those reports in nanorystalline pure Al by molecular dynamic simulations.