Abstract: A new method for measurement of the nonlinearity parameter B/A of liquids by means of photoacoustic pulses is described. The photoacoustic pluse is generated by focused laser pulse via laser-induced breakdown mechanism in liquids. In the distance range, in which the photoacoustic pulses have been measured, the variation of the amplitude of photoacoustic pulse with propagation distance is very close to the spherical attenuation law. From the variation of the rise time of photoacoustic pulse wavefront after a propagating a certain distance, the parameter B/A of liquid is determined. Comparing with the plane pulsed wave with restricted beam, the effect of diffraction may be avoided by using the spherical pulsed wave. The nonlinearity parameter B/A of water is obtained by the present method. The results are reasonably good.