Abstract: Receiver initial phase biases are significant in integer ambiguity resolution. Based on a study of Beidou receiver Initial phase bias, we derived calculation formulas of single-difference-between-receivers (SDBR) inter-frequency receiver initial phase biases. The analysis results using zero-baseline data indicate that the SDBR inter-frequency receiver initial phase biases do not vary with the satellite elevation angles, which suggests that the biases have a short-time stability. When the receiver is just beginning to track satellites, a certain time is needed for the SDBR inter-frequency receiver initial phase biases to be stabilized. The SDBR inter-frequency receiver initial phase biases are changed after the receiver restarts to track satellites, indicating that the biases do not have a long-time stability. The SDBR inter-frequency receiver initial phase biases on the same combination of two frequencies are nearly identical for different satellites.