Objective To investigate the factors affecting 24-hour high blood lactate in patients with septic shock. Methods A total of 150 patients with septic shock admitted to our department of critical care medicine from July 2014 to April 2019 were enrolled in this study. According to their blood lactate level within 24h, they were divided into control group (<4mmol/L, n=75) and observation group (≥4mmol/L, n=75). Their demographic data, clinical data and results of laboratory tests were collected. SPSS statistics 22.0 was used for data analysis. Cox regression model was used to analyze the factors affecting 24h lactate level. Kaplan-Meier survival analysis was employed to draw survival curve and compare the survival rate between the two groups. Results The results of multivariate Cox proportional-hazards regression analysis showed that the score of acute physiology and chronic health evaluation (APACHE Ⅱ) was an independent risk factor (HR=1.452,95%CI 1.103－1.901, P=0.008), while albumin level was an independent protective factor (HR=0.889,95%CI 0.886－0.999, P=0.001) for early hyperlactaemia in septic shock patients. Kaplan-Meier survival curve indicated that the 28-day cumulative survival rate was significantly lower in the observation group than the control group (χ²=15.632, P<0.001). Conclusion Blood lactate level within 24h can effectively evaluate the prognosis of septic shock patients. Higher APACHEⅡ score and lower albumin level are the important factors influencing the increase of lactate level.