The nonlinear optical properties of 1-(2-pyridylazo)-2-naphthol film were studied by using Z-scan technique with ps pulse laser at 532 nm. Under the condition of the lower input pulse enrgy, the resonance third-order nonlinear susceptibility χ(3)R and nonlinear absorption coefficient β were measured to be 1.29×10-9 esu and 42 cm/GW, respectively. The nonlinear absorption responding to the pulse energy was studied and it was found that the reverse saturable absorption turns into the saturable absorption with the increasement of pulse energy.