Abstract: The level of a symbol information in a symbol-sync part transmitted for the purpose of synchronizing a receiver of a digital radio communications system reflects the state of the concurrent transmission. With this factor taken in account, a symbol determining method is provided which comprises the steps of receiving a symbol information extracted from a symbol-sync part of a received signal obtained by demodulating a received wave and digitizing it; generating thresholds for use to determine the value of the received symbol based on the reception level of the symbol information; determining the value of the received symbol in the data part of the received data based on the thresholds; and reproducing the symbol. Therefore, even if a received symbol is deteriorated due to a degradation, etc. of transmission line, a symbol determination can be done with no degradation of the signal reception due to a narrowing of noise margin, etc.