The invention discloses a downlink data decoding method and a device thereof. The method comprises the following steps that: a terminal determines the auxiliary public pilot frequency channel transmitting power of an auxiliary cell where the terminal is arranged according to the obtained cell information, wherein the cell information carries a first power ratio and/or information on whether an MIMO (Multiple Input Multiple Output) pilot frequency way of a main and auxiliary public pilot frequency channel is adopted in the downlink direction of a main cell where the terminal is arranged, and the first power ratio is the ratio of the auxiliary public pilot frequency channel transmitting power of the main cell where the terminal is arranged to main public pilot frequency channel transmitting power; and the terminal carries out downlink data decoding by using the auxiliary public pilot frequency channel transmitting power of the auxiliary cell. Through the downlink data decoding method and the device thereof, provided by the invention, the accuracy in downlink data decoding is improved.