In the Global Positioning System (GPS), the receiver hardware-induced code and phase biases are important factors affecting precise timing, precise modeling of ionosphere and un-difference ambiguity resolution. In the estimation and modeling of ionospheric electron content, it is generally assumed that the GPS receiver hardware biases are constant amounts, without considering the possible fluctuations and influencing factors. Therefore, to analyze the time-varying characteristics of receiver hardware biases can help improve the accuracy and reliability of the ionospheric electron content estimation. In this paper, the time-varying characteristics of single-epoch and single-day solved GPS receiver differential code bias (DCB) and differential phase bias (DPB) are analyzed, and the correlation between the variation of receiver hardware delay and the change of ambient temperature is explored experimentally. The results indicate that receiver DCB will mutate after a restart. And after restarting, the receiver DCB and DPB have a changing process, which takes about 25 min, afterwards they keep stabilized. Also, it's worth noting that the receiver DCB and DPB cannot be stable for a long time. The experimental results show that the change of receiver DCB and DPB can reach about 0.8 m and 4 mm in 2-3 h. In addition, the fluctuation of receiver hardware delay has a strong correlation with the change of the vicinity temperature.