Objective To evaluate the diagnostic performance of ultrasound attenuation analysis （USAT） for quantifying hepatic steatosis in metabolic dysfunction-associated steatotic liver disease （MASLD）， the CT liver-to-spleen attenuation ratio （CT_L/S） was used as the reference standard. Methods In this prospective study， we consecutively enrolled adult participants who were clinically suspected of having MASLD and healthy control volunteers. All participants underwent both USAT imaging and non-contrast CT during the same visit. The repeatability of USAT measurements was evaluated using Bland-Altman analysis and the intraclass correlation coefficient （ICC）. The association between USAT values and the grade of hepatic steatosis was analyzed by means of Spearman′s rank correlation. Factors influencing USAT values were explored through linear regression analysis. The diagnostic accuracy of USAT was determined via receiver operating characteristic （ROC） curve analysis and compared with a clinical prediction model using the DeLong test. Results Among the 268 enrolled participants， CTL/S grading identified 64 individuals with normal liver and 204 with MASLD， which included 78 cases of mild， 69 cases of moderate， and 57 cases of severe steatosis. Bland-Altman analysis and ICC assessment demonstrated excellent agreement for USAT measurements. USAT values were strongly inversely correlated with CTL/S （r = -0.850， 95%CI： -0.880 - -0.813） and strongly positively correlated with steatosis grade （r = 0.846， 95%CI： 0.807 - 0.878； both P < 0.001）. The median USAT value increased progressively as the severity of steatosis increased： 0.55 dB/cm/MHz （normal liver）， 0.67 dB/cm/MHz （mild steatosis）， 0.77 dB/cm/MHz （moderate steatosis）， and 0.86 dB/cm/MHz （severe steatosis）， with significant inter-group differences （all P < 0.001）. Based on simple and multiple linear regression analyses， fatty liver grading was found to be the determining factor for USAT. The optimal USAT cut-off values for detecting mild， moderate， and severe steatosis were 0.61， 0.71， and 0.82 dB/cm/MHz， respectively， yielding areas under the curve （AUCs） of 0.90， 0.88， and 0.87， which were significantly superior to those of the clinical prediction model （DeLong test， all P < 0.01）. Conclusions USAT， a non-invasive， practical， and novel technique， offers both qualitative and quantitative assessment of hepatic steatosis in MASLD. It has significant potential for broad adoption in screening and quantifying hepatic fat content.