IntroductionThe active-fluidics system is a new irrigation system of phacoemulsification that automatically detects and maintains stable intraocular pressure at the set value. This trial is designed to compare the efficacy, visual outcomes, safety and patients’ subjective perceptions of cataract surgery with the active-fluidics system and gravity-fluidics system.Methods and analysisThis trial will recruit 110 patients with age-related cataract at the Chinese People’s Liberation Army (PLA) General Hospital (Beijing, China) and they will be randomly assigned to the active-fluidics group and gravity-fluidics group in a ratio of 1:1 to have phacoemulsification. Patients will be followed up at 1 day, 1 week, 1 month and 3 months postoperatively. The primary outcomes are the cumulative dissipated energy and best corrected visual acuity. Secondary outcomes include: estimated fluid usage, U/S time, total aspiration time, intraocular pressure, corneal endothelium parameters, retinal thickness, macular superficial vessel density, pain scores, scores of the Cataract surgery Patient-Reported Outcome Measures Questionnaire and the complication rates. The data will be independently analysed by the statistical team, who will be masked for the allocation information as participants are.Ethics and disseminationThis study was approved by the Ethics Committee of Chinese PLA General Hospital (approval no. S2021-068-01). Informed consent will be obtained from each participant. All the results will be published in peer-reviewed journals and used for scholarly communication or technical guidance. Protocol version 1.0.Trial registration numberChinese Clinical Trial Registry (ChiCTR2100044409).