Background:The ACTS-GC study had shown postoperative adjuvant therapy with S-1 improved survival of patients with locally advanced gastric cancer.Addition of oxaliplatin to S-1 is considered to be acceptable as one of the treatment options for gastric cancer patients after radical gastrectomy with D2 lymph node excision.Methods:We have commenced a randomized phase III trial in December 2016 to evaluate S-1 plus oxaliplatin compared with S-1 alone in the adjuvant setting for locally advanced gastric cancer.A total of 564 patients will be accrued from 13 Chinese institutions in two years.The primary endpoint is 3-year relapse-free survival.The secondary endpoints are 5-year overall survival,proportion of patients who complete the postoperative chemotherapy and incidence of adverse events.Ethic and dissemination:The trial has been approved by the institutional review board of each participating institution and it was activated on December,2016.The enrollment will be finished in December,2018.Patient’s follow-up will be ended until December,2023.Trial registration:Clinical Trials.gov,identifier:NCT02867839.Registered on August 4,2016. Background:The ACTS-GC study had shown postoperative adjuvant therapy with S-1 improved survival of patients with locally advanced gastric cancer.Addition of oxaliplatin to S-1 is considered to be acceptable as one of the treatment options for gastric cancer patients after radical Gastrectomy with D2 lymph node excision.Methods:We have commenced a randomized phase III trial in December 2016 to evaluate S-1 plus oxaliplatin compared with S-1 alone in the adjuvant setting for locally advanced gastric cancer.A total of 564 patients will be Accrued from 13 Chinese institutions in two years.The primary endpoint is 3-year overall-lapse survival.The secondary endpoints are 5-year overall survival, proportional of patients who complete the postoperative chemotherapy and incidence of adverse events.Ethic and dissemination:The Trial has been approved by the institutional review board of mutually participating institution and it was activated on December,2016.The enrollment will be finished in December,2 018. Patient’s follow-up will be ended until December, 2023. Trial registration: Clinical Trials.gov, identifier: NCT02867839. Registered on August 4, 2016.