This paper presents a method for Lamb wave tomography utilizing a quantitative laser ultrasound visualization technique. Lamb wave tomography had been made for image restructuring of the defect region information of specimen, including position, size and shape. Previous researches developed existing algorithm to restructure image in Lamb wave tomography. However these restructured algorithms are susceptible to refraction, strong scattering or abrupt change in the thickness and result inaccurate image reconstruction. This paper employs experimental method named offset grid scan for Lamb wave propagating along samples and extracts the group velocity of Lamb wave using π -point phase comparison signal processing. The goal of the offset grid scan in a very short temporal domain presented in this study is to counteract the above problem lead to various errors. In this research, the experimental method with the numerical results is more accurate than previous algorithms.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.