Objective To compare the sensitivity and specificity of different process evaluation indexes or index combinations in the diagnosis of feeding intolerance in critically ill children. Methods The energy intake and feeding intolerance process evaluation indexes of 196 critically ill children were collected within 5 days before the start of nasal feeding. By comparing the sensitivity and specificity, the diagnostic ability of single index or index combinations was analyzed. Results The diagnosis of feeding intolerance was made when the children′s energy intake through enteral nutrition did not reach 2/3 (criterion 1) or 80% (criterion 2) of target energy within 5 days after starting enteral nutrition. Among the 7 process evaluation indexes, the area under ROC for gastric retention and vomiting alone was ＞0.7. Against diagnostic criterion 1 (2/3 of the target energy), the sensitivity and specificity of gastric retention stood at 94.28% and 73.91%, respectively; against diagnostic criterion 2 (80% of the target energy), the sensitivity and specificity of gastric retention plus vomiting stood at 90.83% and 68.70% respectively. Conclusion In the diagnosis of feeding intolerance in critically ill children, the single index of gastric retention or the combination of gastric retention and vomiting are preferred, which may help early identification of feeding intolerance in the children and boost implement of enteral nutrition therapy.