Matrix formalism is applied in the theory of optical detection of picosecond acoustic strain pulses in anisotropic multilayers, probed by oblique incident laser radiation. A 4×4 matrix formalism, which can be easily implemented in computer programs, is presented to calculate the 2×2 transient reflection matrix of the sample. Transient reflectometric and interferometric signals can be readily calculated from the transient reflection matrix. In addition, the rotation of the polarization state of the reflected probe induced by acoustic waves is also readily accessible. Therefore, the simulation of all the time-resolved picosecond ultrasonic experimental signals can be simulated in a single straightforward procedure. This matrix formalism is applied to treat the problem of shear wave detection within an isotropic sample.