Abstract: Elastic parameters such as Young’s modulus and Poisson’s ratio are critical indicators for evaluating the mechanical properties of materials. To address the limitations of conventional ultrasonic methods, such as their reliance on piezoelectric transducers, coupling media, and specimen geometry, this work proposes a fully optical method for measuring elastic constants based on laser ultrasonics. Considering the advantages of laser ultrasonics, including non-contact operation, high responsiveness, wide bandwidth, and strong robustness, the method enables high-precision and nondestructive characterization of solid materials. Narrowband surface acoustic waves are generated via the transient thermal grating mechanism, and their velocities are determined using the known surface wave wavelength and central frequency. Longitudinal wave velocities are obtained using a coaxial transmission and detection configuration. Based on the theory of elasticity, the measured wavespeeds are used to invert the material’s Young’s modulus and Poisson’s ratio. Experimental results show deviations of approximately 3% from theoretical values, with repeatability errors within 0.5% across multiple samples. These findings confirm the feasibility and reliability of the proposed method, which holds promise for real-time characterization of elastic properties in materials with complex structures.