Introduction Acute primary angle closure (APAC) is a common ophthalmic emergency for Chinese patients causing potential visual disabilities. According to current guidelines published by developed countries, a stepwise protocol (medication laser or paracentesis surgery) is recommended for emergency management of APAC. However, patients with APAC in China and developed countries differ in disease characteristics as the Chinese have longer attack duration and lower success rate in breaking the attack with solely medication or laser therapy. It has been proved that long attack duration is a risk factor for failed medical or laser therapies in subsiding APAC. Since prompt and effective treatment is pivotal in preserving visual function as well as avoiding APAC-induced blindness, direct trabeculectomy may largely benefit long-attacking patients with APAC in China.Purpose The Long-Attacking Acute Angle Closure study aims to compare long-term visual function and safety after different initial treatment strategies: direct surgery (trabeculectomy) or stepwise protocol for patients with APAC with attack duration longer than 72 hours.Methods and analysis This is a pragmatic, multicentre, randomised controlled trial targeting Chinese patients with APAC duration longer than 72 hours. Eligible participants will be identified at either emergency department or glaucoma clinics, then randomised into stepped treatment group or trabeculectomy group using a computer central randomisation service. The patients will be followed up for 1 year after initial treatment.Main outcomes and measures The primary outcome is logMAR BCVA 1 year post initial treatment. Secondary outcomes consist of complete success rate in breaking the attack, intraocular pressure value, mean deviation on Humphrey visual field testing and vision-related quality of life collected using the National Eye Institute Visual Function Questionnaire (25 items) 1 year post initial treatment.Trial registration number ChiCTR2200057289.