Background: Past studies have found that sodium bicarbonate ingestion prior to exercise has a performance-enhancing effect on high-intensity exercise. The aim of this study was to investigate the effects of continuous sodium bicarbonate (NaHCO 3 ) supplementation on anaerobic performance during six weeks of high-intensity interval training (HIIT). Methods: Twenty healthy college-age male participants were randomly assigned to either the HCO 3- group (SB) or the placebo group (PL), with 10 subjects in each group. Both groups completed 6 weeks (3 days/week) of HIIT with the SB ingesting an orange-flavored solution containing 15 g xylitol and 0.2 g HCO 3- /kg body mass during each training day, and PL ingesting a similar beverage that was HCO 3- -free. This study separated 6 weeks of training into two stages with different training intensities, with the first 3 weeks at a lower intensity than the second 3 weeks. Blood samples to measure serum HCO 3- were obtained 5 min before and 30 min after the following HIIT training sessions: Week 1, training session 1; week 3, training session 3; week 6, training session 3. Three 30s Wingate tests (WAnT) were conducted before, in the middle, and after the training and the supplementation interventions, with peak power, mean power, and fatigue index obtained during WAnT, and blood lactate and heart rate obtained after WAnT. Results: Our findings indicate the following: 1) Serum HCO 3- level of SB was significantly higher than PL (p < 0.05) both before and after each HIIT; 2) Relative peak power in WAnT was significantly higher in the SB group after 6 weeks (p < 0.01); 3) Lactate clearance rate and the lactate clearance velocity after 10 min of WAnT were both significantly higher in SB in the post-test (p < 0.01); 4) Heart rate recovery rate at 10 min after WAnT in both SB and PL after 6 weeks were significantly improved (p < 0.01 and p < 0.05, respectively), resulting in no difference between groups on these measures. Conclusions: These data suggest that supplementation of HCO 3- at the level of 0.2 g/kg body mass before HIIT training enhances the effect of HIIT on anaerobic performance, and improves the blood lactate clearance rate and the blood lactate clearance velocity following anaerobic exercise.