This final project aims to determine the effect of trust, commitment, communication and conflict handling as a key factor in relationship marketing either partially or simultaneously on customer loyalty PT Bank Pembangunan Daerah Jawa Tengah Cabang Koordinator Pati. The method to collect the data in this research uses questioner, interview and literature review. In this study used non-probability sampling method with a sampling technique incidental sampling. This research took 100 respondents. The technique analysis are validity and reliability test, classic assumption test, multiple linear regression, t test, F test and coefficient of determination by using SPSS 22.0. The result of multiple linier regression analysis could be shown by the regression equation Y= 4,616 + 0,295 X1 + 0,174 X2 + 0,169 X3 + 0,293 X4 + e. Coefficient of determination in this research was 0.584, which meant that relationship marketing variable consisted of trust, commitment, communication, and conflict handling influence of customer loyalty is 58.4%, whereas the remaining 41.6% is influenced by other variables which are not observed in this research. The result of the research shows that trust, commitment, communication and conflict handling had positive and significant influence at the same time toward customer loyalty. Trust variable has the greatest influence on customer loyalty.