Abstract: To enhance accuracy and convenience in psychological crisis assessment in children and adolescents, 48 346 primary and secondary urban school students were recruited for a psychological crisis survey via big data cloud platform．The survey data were used to build and verify a comprehensive grading system for psychological crisis assessment．A total of eight physical and mental symptom indicators and five level crisis assessment standards were included in the system．Compared with assessment by single symptom index, comprehensive assessment by eight symptoms showed a higher level of consistency with secondary assessment．The new system reflects overall mental health and crisis concern level more accurately in primary and secondary school students．This work will be helpful for school management to identify early student psychological problems to carry out targeted hierarchical interventions．