Objective To explore the change of plasma D-dimer (DD),lactate dehydrogenase isoenzyme 3 (LDH3),tissue plasminogen activator (t-PA) in the early stage of acute pulmonary embolism and their clinical significance.Methods Forty-six patients with acute pulmonary embolism of early stage (pulmonary embolism group) and 50 cases of normal person (control group) were enrolled in this study.The patients in pulmonary embolism group were divided into low-risk(18 patients),middle-risk(15 patients) and higher-risk (13 patients).The levels of DD,LDH3 and t-PA were detected and compared.Results The levels of DD,LDH3 and t-PA in pulmonary embolism group were (2.95 ± 0.73) mg/L,(421.42 ± 63.29)U/L and (0.85 ±0.02) U/L,and significantly higher than those in control group [(0.03 ±0.01) mg/L,(198.17 ± 23.37) U/L and (0.59 ± 0.02) U/L] (P ＜ 0.05).The levels of DD,LDH3 and t-PA in low-risk patients [(1.49 ± 0.04) mg/L,(315.47 ± 38.24) U/L and (0.63 ± 0.01) U/L] were significantly lower than those in middle-risk patients [(2.22 ±0.27) mg/L,(382.41 ±54.36) U/L and (0.79 ±0.02) U/L] and higher-risk patients [(3.38 ± 0.98) mg/L,(583.93 ± 117.21) U/L and (0.92 ± 0.03) U/L] (P ＜ 0.05).The levels of LDH3 and t-PA in middle-risk patients were significantly lower than those in higher-risk patients (P ＜ 0.05).After treatment,the levels of DD,LDH3 and t-PA were significantly decreased [(2.95 ± 0.73)mg/L vs.(1.03 ±0.11) mg/L,(421.42 ±63.29) U/L vs.(223.24 ±25.04) U/L,(0.85 ±0.02) U/L vs.(0.62 ± 0.02) U/L] (P ＜ 0.05).Conclusions The levels of DD,LDH3 and t-PA in the early stage of acute pulmonary embolism are increased significantly,and with the remission of the patient's condition,the levels of DD,LDH3 and t-PA are decreased.United detection conduces to the diagnosis of acute pulmonary embolism.