This is a multicenter clinical study to evaluate the safety and efficacy of golidocitinib in patients with primary immune thrombocytopenia (ITP). The study consists of two parts: Part A dose escalation and Part B dose expansion. Part A is designed to obtain the safety profile of golidocitinib in patients with ITP and the recommended dose for the randomized cohort in Part B. Part B is a randomized, double-blind, placebo-controlled study, and the primary objective of this part is to evaluate the preliminary efficacy of golidocitinib in patients with ITP.