Abstract: Objective To quantitatively evaluate the stiffness of spastic biceps brachii muscle (BBM) at different angles of elbow flexion and in different muscle layers by real-time shear wave ultrasonic elastography. Methods From May 1,2019 to January 20,2020,20 patients with post-stroke hemiplegia admitted to the First Medical Center of Chinese PLA General Hospital were included in our study.Of the 20 cases,there were 16 males and 4 females with average age of 53.8 (range,30-75) years.The difference of Young's modulus between the affected BBM and unaffected BBM,BBM at 90° elbow flexion and BBM at 0° elbow flexion,and superficial and deep BBM were compared quantitatively by real-time shear wave elastography. Results The Young's modulus of the affected BBM was significantly higher than that of the unaffected BBM (Md:superficial muscle 57.2 vs 31.0,P<0.01;deep muscle 74.2 vs 32.5,P<0.01) at 0° elbow flexion;the Young's modulus of spastic BBM at 90° elbow flexion was significantly lower than that of spastic BBM at 0° elbow flexion (Md:superficial muscle,39.1 vs 57.2,P<0.01;deep muscle,42.6 vs 74.2,P<0.01);and the Young's modulus of superficial BBM was significantly lower than that of deep BBM (Md:57.2 vs 74.2,P<0.01) at 0° elbow flexion.At 0° elbow flexion,the Young's modulus in the superficial and deep layers of BBM was positively correlated with MAS score (superficial,r=0.612,P=0.004;deep,r=0.732,P=0.000). Conclusion The real-time shear wave ultrasound elastography can evaluate the stiffness of spastic BBM after stroke.