Zinan Temple is one of the Taoist temples in Taiwan, demonstrating the vital status of religious activities and beliefs. Creating religious products that tourists like through unique religious resources and conducting product differentiation competitions is essential for religious tourism to attract tourists. The research used a convenience sampling method, and 377 online questionnaires were distributed and used SPSS 21.0 to conduct linear regression. This research affirms the positive effect of product attachment on loyalty through indispensability and irreplaceability, as well as irreplaceability being a more critical intermediary variable. This research has verified the theoretical impact of religious tourism products on loyalty and makes specific recommendations on improving Taoist tourists’ loyalty to enhance the tourism competitiveness of Zinan Temple. Therefore, this research provides practical suggestions for religious development and cultural sustainability.