In this present work, we propose a new method to remove the parasitics contribution to the VCSEL chip response, in order to obtain the intrinsic transmission behavior. It has been observed that the S 11 reflection coefficient of the chip is only due to the electrical access to the chip composed by the transmission line and cavity contacts. This allows us to decompose the chip into two cascaded subsystems representing the electrical access and the optical cavity respectively. An equivalent electrical circuit is developed for the electrical access behavior and, combined with the transfer matrix formalism, it becomes possible to remove the parasitics contribution from the measured S 21 response. In this way, the intrinsic 3-dB bandwidth of the VCSEL can be determined.