Objective To investigate the application value of modified early warning score (MEWS) for assessment of patients in pre hospital first aid.Methods For patients with MEWS method in 3 478 cases of pre hospital first aid,scored in 0-4,5-9 and ≥ 10 points.Analysis of the relationship between the distribution and severity in patients with different grades,and tracing the fate and the condition of patients after admission.Results In MEWS patients with low 0-4 points was divided into pre hospital first aid,accounted for 69.18％ (2 406/3 478),severe cases accounted for 2.58％ (62/2 406); MEWS 5-9 accounted for 21.54％ (749/3 478),severe patients increased to 37.92％ (284/749); MEWS ≥ 10 points accounted for only 9.29％ (323/3 478),severe patients increased to 87.00％ (281/323).MEWS scores higher ratio in patients with severe more,MEWS 5-9 points,severe patients with MEWS ≥ 10 points 0-4 critical patients proportion (P ＜ 0.01).MEWS 5-9 points,≥ 10 points patients admitted to a specialist ward and intensive care units treatment compared with MEWS 0-4 points patients increased significandy (P ＜ 0.01),the mortality rate was also significandy increased (P ＜ 0.01).Conclusion The MEWS method in pre hospital first aid to early warning of potential in critically ill patients,the higher score,the more serious condition,the higher mortality rate.