Objective: To assess the effects of Shenfu Injection ((sic), SFI) on blood lactate, and secondarily its effect on the lactate clearance (LC) in patients with post cardiac arrest syndrome (PCAS). Methods: The present study is a post hoc study of a randomized, assessor-blinded, controlled trial. Patients experienced in-hospital cardiac arrest between 2012 and 2015 were included in the predefined post hoc analyses. Of 1,022 patients enrolled, a total of 978 patients were allocated to the control group (486 cases) and SFI (492 cases) group, receiving standardized post-resuscitation care bundle (PRCB) treatment or PRCB combined with SFI (100 mL/d), respectively. Patients' serum lactate was measured simultaneously with artery blood gas, lactate clearance (LC) was calculated on days 1, 3, and 7 after admission and compared between groups. Lactate and LC were also compared between the survivors and non-survivors according to the 28-d mortality, as well as the survivors and non-survivors subgroups both in the SFI and control groups. Results: In both groups, compared with pre-treatment levels, mean arterial pressure (MAP) and PaO2 were significantly improved on 1, 3, 7 d after treatment (P<0.05), while heart rate (HR) and blood glucose levels were significantly decreased on 1, 3 and 7 d after treatment (P<0.05). compared with control group, SFI treatment improved the values of MAP and PaO2 (P<0.05), and significantly decreased the levels of HR and the blood glucose level on 3 and 7 d after treatment (P<0.05). Compared with the control group, lactate levels decreased faster in the SFI group versus the control group on 3 and 7 d (P<0.05). From initiation of treatment and the following 3 and 7 d, SFI treatment greatly increased the LC compared with that in the control group (P<0.05). Compared with survivors, non-survivors had higher admission lactate levels (7.3 +/- 1.1 mmol/L vs. 5.5 +/- 2.3 mmol/L; P<0.01), higher lactate levels on days 1, 3 and 7 (P<0.05), and LC were decreased significantly on 3 and 7 d after treatment (P<0.05). Similar results were also found both in the SFI and control groups between survivors and non-survivors subgroups. Conclusion: SFI in combination with PRCB treatment is effective at lowering lactate level and resulted in increasing LC in a targeted population of PCAS patients.