Violin was made in 16th century and it becomes an important role in music history. Holding a violin is the first lesson to learn violin and this is a constrained activity. Playing violin in a poor posture will affect the ability and quality of performance and also lead muscles occur disorders. Literature review pointed out that upper trapeziuses are the related muscles used while playing violin and proved that the performance of playing with a shoulder rest is greater than without it. However, none of any researches study how the different combination of height variation of the two feet affect the muscles and whether a relationship between the anthropometry. In this study, human factors, is an engineering technique and an interaction research about human and working environment, is applied to investigate the effect on upper trapeziuses with different shoulder rest height and anthropometry. Twenty subjects were invited to participate and twelve shoulder rests provided to be tested. Surface electromyography was used to collect the left and right upper trapezius (LUT and RUT) muscle activities. The Friedman test results showed there were significant differences within twelve shoulder rests and it indicated that the variation height of shoulder rest’s feet could affect the left and right upper trapezius. The relationship between the two shoulder rest height (Y1 and Y2) and the shoulder and neck length (X1 and X2) were found by applying multiple linear regression and finally, four equations were obtained to use for predicting Y1 and Y2 in doing task two (Slow Task) and task three (Fast Task). These results provide a method and reference on choosing the most comfortable shoulder rest height on LUT and RUT while playing violin in different situation.