This article focuses on the ionizing total dose effects of the analog integrated circuits in space radiation environments and the corresponding hardening strategies based on the standard bipolar process.The irreplaceable core role of analog circuits in spacecraft is discussed，the physical mechanisms of the ionizing total dose effects and their degeneration mechanisms on bipolar circuits are analyzed，and the necessity of hardening design is emphasized.The circuit hardening methods are elaborated in detail.Taking the operational amplifiers and voltage reference as examples，the degradation mechanisms of the total ionizing dose effects and the key points of the hardening design are specifically analyzed.The results show that，without designed hardening，the operational amplifiers based on the standard bipolar process will experience serious parameter deviations under the total ionizing dose of 30 krad（Si） （1 rad = 0.01 J/kg）.Conducting circuit hardening design for sensitive parameters can enhance the space radiation tolerance of bipolar analog circuits，which is of great significance for ensuring the long-term reliable operation of spacecraft.