Objective To discuss the effect of evaluation before surgery,the tolerance of surgery and risk after surgery.Methods The analysis was conducted through random selection of 80 cases of pa-tients admitted by the hospital and had cardiothoracic surgery on other day.Patients were divided into 3 groups,respectively pulmonary function test normality,damage mildly and moderately and damage severely. Patients were observed in rest state,after motion,after motion in 2 minutes,4 minutes and 6minutes for their blood gas analysis.Results ⑴ PaO2 ,PaCO2 and SaO2 of patients in the second group changed after motion,however,the discrepancy between the two groups was not significant statistically(P >0.05 ). PaO2 and SaO2 of patients in the second group changed a lot after motion,the discrepancy between the two groups was significant statistically(P <0.05).The discrepancy of PaCO2 between the two groups was not significant statistically(P >0.05).⑵ In rest state,SaO2 was no more than 90% and 100%(4 /4)of pa-tients had complication .After motion,SaO2 was no more than 90% or the descend range of it was no less than 4%.90.0%(9 /10)of patients had complication,92.8%(13 /14)in total.SaO2 was more than 90%in rest state and after motion or the descend range was less than 4%.10.6%(7 /66)of patients had compli-cation after surgery.the discrepancy between the two groups was significant statistically(P <0.01).Con-clusions Dynamic blood analysis of pulmonary function test can better forecast cardio-pulmonary function, risk of surgery and past -operative recovery of patients,the index with most value is SaO2 of arterial blood gases after motion(0 min).