Objective To assess the clinical value of lung ultrasound (LUS) B-lines in diagnosis of rheumatoid arthritis (RA) associated interstitial lung diseases (RA-ILD).Methods Forty-five consecutive patients with RA who underwent a high resolution computed tomography (HRCT) scan of the chest,were also examined by LUS for detection of B-lines(within 1 month independently in all patients).The B-lines score was obtained by summing the number of total 50 inter-costal spaces (ICSs) of chest wall.Pulmonary fibrosis was quantified by HRCT as previously described by the 30-point Warrick score.Results B-lines score significantly correlated with the Warrick score [(r=0.778,95％CI(0.627,0.872),P＜0.05].Receiver operating characteristic (ROC) curve confirmed that B-lines cut-off point 77[sensitivity of 100％,specificity of 64.3％ respectively,area under curve [AUC] =0.86,95％CI(0.724,0.945)] and 108[sensitivity of 90％,specificity of 88.6％ respectively,AUC=0.879,95％CI(0.747,0.957)] had an optimal power to discriminate mild (Warrick score＜8) and severe fibrosis (Warrick score＞15):Conclusion The data confirm that LUS is a useful technique to identify ILD in RA.In RA-ILD,B-lines correlate significantly with HRCT and are able to identify mild and severe degree of fibrosis.LUS is a promising non-invasive and non-ionizing strategy for screening RA-ILD.