A Base Station (BS) communication module and a Customer Premise Equipment (CPE) communication module are adapted to implement a method for selecting a Modulation and Coding Scheme (MCS). The method for selecting an MCS includes the following steps: receiving a plurality of first packets in a first period, and calculating a Packet Error Rate (PER); determining whether the PER is greater than an error rate threshold; and when the PER is greater than the error rate threshold, performing the following steps: obtaining a Carrier to Interference plus Noise Ratio (CINR) return value; performing an adjusting procedure to obtain a CINR adjustment value; calculating an actual return value according to the CINR return value and the CINR adjustment value; and selecting one of a plurality of MCSs according to the actual return value.