ABSTRAK
This descriptive qualitative research examines social solidarity of the Chinese and Javanese (pesantren) ethnic groups in Lasem. Both Chinese and Javanese ethnic groups live side by side safely and peacefully, thus creating a harmonious life. The aim of this research is to explain the mechanical and organic solidarity between the Chinese and the santris living in the pesantren (Islamic Boarding School) in Kauman, Lasem. The research result indicates that organic solidarity can be seen when these two ethnic groups help each other in various activities. For example, in the haul (commemoration of the death of a person) of Mbah Sambu held by the Kauman Islamic boarding school, the Chinese ethnic gave support both morally and materially. Similarly, when the Chinese ethnic commemorate their feast days, they will receive support from the pesantren.