Square root-raised-cosine (SRRC) filters are used in many systems for spectrum shaping, which leads to a high peak-to-average power ratio (PAPR). Nevertheless, some applications demand a low PAPR in terms of both the error performance and the strict restriction of the spectrum mask. In this letter, we propose a PAPR reduction method based on the modified active constellation extension for systems using SRRC filters. Results show that the proposed method substantially reduces the PAPR, and therefore it is applicable to satellite communications to improve the power efficiency at the transmitter.