A quantitative assessment method of spasticity based on the fusion of acceleration and angle signals is proposed and corresponding device is developed to solve the difficult problem of accurate quantitative assessment of spasticity in stroke patients. By analyzing the limb acceleration and joint angle signal data, the joint angle (θp) and joint mobility (θrom) corresponding to the acceleration mutation point are extracted, and the θp/θrom value is calculated for the evaluation of spasticity status. The modified Ashworth scale (MAS) and the device were used in clinical experiments on 27 subjects, and different spasm detection methods were used for different muscle groups. The correlation analysis between MAS level and θp/θrom value shows that θp/θrom value can be used to assess spasticity state, and the device has good validity, the correlation meets r=-0869, P<005. Based on MAS and θp/θrom values, the MAS grade indicating spasticity state was modified again. The results showed that there was significant difference between the modified MAS grades (P<0001), which could realize quantitative evaluation of spasticity state.