When the surface of a specimen is ablated by a linear laser source,the directivity of laser ultrasound Rayleigh surface wave is studied. Based on the ablation mechanism of laser ultrasound,laser ablation is regarded as a normal stress. According to the displacement of a particle in the far field,the directivity function of Rayleigh surface wave is given. A set of laser ultrasound transmitting and receiving system was built,and the amplitude-frequency characteristics of the obtained signals were analyzed to verify the correspondence of signal center frequency and transducer center frequency. The directivity pattern corresponding angles were drawn in the polar coordinate system by using peak to peak value,and then the factors affecting the measurements of directivity patterns are discussed. The results show that the directivity function has a reference value for laser ultrasonic testing and inspection by using Rayleigh surface wave.