Due to its advantageous properties, the critically refracted longitudinal waves (LCR) are used in various fields of nondestructive evaluation, especially for residual stress measurements. However, although many researches use these waves, the characteristics of the LCR beams are not completely understood to date. This paper contributes to clarify in a complete way and gives numerical and experimental analysis of the ultrasonic beam of the LCR waves generated by a transducer. It also answers questions about the parameters that influence its beam profile and therefore allow performance optimization when used for NDE and NDT applications. First, beam particle displacement components are numerically calculated in both tangential (surface) and normal (depth) directions; the reflectivity diagrams are then deduced. The experimental study is also used to confirm the numerical results. Numerical and experimental studies have shown that the displacement of the LCR waves at the surface follows a constant law, which does not depend on the frequencies of the sensor. On the other hand, it is shown that the incidents angles, the aperture diameter and the center frequency are the most important factors in controlling the directivity and subsequently the position of the main lobe of the LCR waves.