The super-hydrophobic aluminum surface is prepared by picosecond laser, and the effect of number of laser pulses on the surface morphology and wettability of samples is investigated. With the increment of number of pulse, the surface microstructure of samples transforms gradually from regular nano-stripped one to micro-nano-hybrid one, and the surface roughness first increases and then decreases. When the number of pulses is 177, the roughness is the maximum (3.855 μm). After laser processing, the surface wettability of samples first appears super-hydrophilic. But after a process with a heat preservation at 100 ℃ of 24 h, it becomes hydrophobic or even super-hydrophobic. The surface wettability transformation of samples is the joint action result of both the surface morphology and the chemical elements.