According to related setting calculation guide, the impedance criterion of loss of excitation (LOE) protection should be verified to make sure LOE protection operates before under excitation limit (UEL) control. However, the setting values of LOE and UEL are calculated separately, and their operation characteristics are defined in different coordinate systems, leading to the mismatch of each other easily. Considering the steady state stability impedance criterion commonly used for large hydro-generators LOE protection, this paper presents an algorithm of comparing the operation zone of LOE and UEL with the concern of specific protection device. Furthermore, the paper investigates the coordination relationship between LOE protection and UEL control. At last, several schemes are given on better cooperation of UEL with LOE impedance criterion on stator side.