Abstract: Objective To explore the phenotype-genotype correlation of X-linked agammaglobulinemia（XLA） between clinical and immunological phenotypes and gene cDNA mutaions. Methods Using anti-BTK monoclone antibody the expression level of BTK protein was measured by flowcytometry. The BTK mutations in XLA patients were detected using PCR and direct sequencing. Some of the patients′ mother and relatives were also taken BTK mutation analysis. Results ①Forty of 50 XLA patients were identified to have BTK gene mutation.The major types of BTK mutation were missense(16 cases) and nonsense mutations(13 cases).②The age of onset of the XLA patients with missense mutations and other mutation were (1.4±1.1) and （1.4±0.7）years（P=0.45). The proportion of missense mutation increased, whereas the proportion of nonsense mutation decreased with the age of onset increasing. ③The numbers of circulating B cells of 34 cases(85%) were below 0.1%; 4 cases were between 1% and 2%. Among these 4 patients, two cases were missense mutation, one case was nonsense mutation and one case was splice-site mutation. Two cases with 2% B cells carried all missense mutiation. ④The major types of BTK mutation of the patients with low levels of serum IgG(<3 g·L-1) were missense mutation and nonsense mutation. ⑤There was no significant difference in exppression level of BTK protein between the patients with missense mutation and patients with other mutation types. ⑥6 of 21 cases with 2031 polymorphism had severe arthritis.Among 19 cases without 2031 polymorphism,3 cases had recurrent arthritis. ⑦28 of 32 mothers (87.5%) were confirmed to be carriers of BTK mutation. Conclusions There was no clear genotype-phenotype correlation in Chinese XLA patients. Missense and nonsense mtation were the most common types of mutation in Chinese XLA patients. Missense mutation may be related to relatively high levels of IgG and expression level of BTK protein. Polymorphic variant (2031T>C) in exon 18 may partly contribute to the clinical phenotype of arthritis.