The purpose of this study is to know the influence of trust on customer loyalty (study case of micro financing product’s at Syariah Mandiri Bank Assistant Branch Office Semarang Karangayu). The methods of collecting data are literatures study and questionnaires to 50 customer. The analysis techiques used are validity, reliability, simple linier regression, normality, t-test, and the coefficient of determination. Analysis of data uses simple linier regression. It is obtained that the regression equation Y equals 5.161 + 0.243X. Trust variables, partially have positive influence on customer loyalty. The coefficient of determination shows that 52.1% customer loyalty influenced by trust variables, while the remaining 47.9% influenced by other variables which are not included in this research. It is recommended that micro finance product’s in Syariah Mandiri Bank Branch Office Semarang Karangayu should increase of trust because it is more influencial.