The prevalence of renal calculi in patients with gout is high. Alkalized urine has been recommended by the 2020 European Association of Urology (EAU) guidelines to promote calculus dissolution. However, randomized controlled trials are lacking.In the protocol of this randomized, placebo-controlled, double-blinded trial, patients with gout combined with renal calculi are randomized (1:1) to the placebo and sodium bicarbonate groups. The intervention would be performed for 24 weeks, the 1-12 weeks are double-blinded, and the 13-24 weeks are open-labeled. Sodium bicarbonate (1 g tid) will be performed for 24 weeks in the sodium bicarbonate group. The placebo will be performed for 12 weeks and not be performed from 13 weeks to 24 weeks in the placebo group. All subjects will be administered febuxostat (40 mg/day) for 24 weeks and receive concomitant anti-inflammatory prophylaxis therapy for 12 weeks. The primary outcome is the proportion of patients whose renal calculus volume will be reduced after 12 weeks of treatment. The secondary outcomes include the volume changes of renal calculi, uric acid changes, the proportion of patients with serum uric acid (sUA) levels < 360 μmol/L, the changes in estimated glomerular filtration rate (eGFR), the pH value of urine, and the incidence of adverse events after treatment for 12 and 24 weeks.This study will evaluate the efficacy and safety of sodium bicarbonate-alkalized urine on renal calculi in patients with gout.ClinicalTrials.gov ChiCTR2100045183. Registered on April 7, 2021, with ChiCTR.© 2021. The Author(s).