Abstract： Objective To investigate correlation between the APACHE II score , arterial blood lactate , serum procal-citonin and prognosis of severe pneumonia.Methods The clinical data of 82 patients with severe pneumonia from 2011 to 2013 were retrospectively analyzed in our hospital.Mortality and survival at discharge were collected.We divided all the patients into two groups according to whether the patients is alive and observed the dynamic change of APACHE II score, arterial blood lactate, serum procalcitonin.Results The survival mortality of severe pneumonia patients at dis-charge were 59.76%and 40.24%.APACHE II score, arterial blood lactate, serum procalcitonin in survival group were (21.85 ±6.50 points), (3.81 ±2.43 mmol/L), (3.68 ±3.09 ng/mL), and were (25.24 ±7.15 points), (5.42 ± 3.76 mmol/L), (5.48 ±4.15 ng/mL) in death group respectively.Significant differences (P<0.05) were found a-mong three groups of data.All data decreased with increasing days of hospitalization in survival groups while the trend was exactly the opposite in death group.APACHE II was positively correlated with arterial blood lactate and serum pro-calcitonin.There are significant differences in three groups of data between the survival group and death group on the third day as well as on the seventh day.Conclusions The dynamic change of APACHE II score , arterial blood lactate , and serum procalcitonin can be one of the references to evaluate the condition and prognosis of patients .