The invention provides a Global Navigation Satellite System (GNSS) receiver. In one embodiment, the GNSS receiver comprises a memory, a buffer, a correlator, and a selector. The memory stores a memory code and outputs a portion of the memory code as a first code segment. The buffer comprises a plurality of component buffers and stores the first code segment into one of the component buffers in order. The selector selects a portion of the first code segments stored in the buffer as a second code segment output to the correlator according to the code phase selection signal, wherein the data length of the second code segment is equal to a correlation data length of the correlator. The correlator calculates a correlation between a received GNSS signal with the correlation data length and the second code segment.