Abstract: This paper discusses three technical problems of the precise SCR automatic temperature control system in practical operations affecting the stability and reliability of the system: the changes in the values and wave shapes of the AC normal mode interference signals inlet by the temperature measuring thermocouple would cause irregular low-frequency oscillation of the control system; the mutual interference between in-phase power supplies and between out-of-phase power supplies during the operation-in-parallel of many SCR control systems would cause follow-up and out-of-control of the system; The breakdown short-circuit of SCR would cause burning-out of the equipment under control. This paper presents detailed theoretical analyses and suggests efficient ways in dealing with those problems so as to enhance the stability and reliability of the precise SCR automatic temperature control system.