The invention relates to a low-power-consumption RFID-tag-based PIE decoding method. The method comprises: (1), a sign bit sequence is decoded; to be specific, a time length standard value for comparison and determination is constructed, a series of processing is carried out on a lead code part of PIE coding, counting is carried out on TART and RTcal by using a system clock period, and the counting value is divided by three to obtain a processing result marked as NP; and (2), counting is carried out on lengths of follow-up PIE symbols; if the length of the symbol behind the RTcal is larger than the twofold NP, determination of TRcal is made; if the length of the symbol is larger than or equal to the NP, the logic is determined to be ''1''; if the length of the symbol is smaller than the NP, the logic is determined to be ''0''; and the follow-up symbol length is equal to the sum of lengths of a continuous high level and low level part; and if the high level length is larger than the fourfold NP, PIE coding is determined to be ended. According to the invention, the system clock frequency can be reduced, so that the power consumption is obviously reduced and the receiving sensitivity is improved.