As hotspots of biocultural diversity (BCD), mountain areas contain the richest ecosystems with cultural characteristics. However, in the context of cultural homogenization and ecological decline, some high-value mountain areas are still not adequately protected, and some protected areas (PAs) even suffer from an imbalance between natural and cultural protection. To improve the coverage and conservation effectiveness of PAs in mountain areas, we propose a BCD evaluation approach to identify conservation gaps and prioritization, taking the Taishan Mountain Area (TMA) as a study case: first, we used four biodiversity factors (topographic diversity, geological diversity, ecosystem services, bird species distribution) and four cultural diversity factors (cultural landscape, intangible cultural heritage, traditional production modes, population and economy) to evaluate the BCD values; second, we generated a map of BCD hotspots and graded them into three levels; and finally, we compared the evaluation result with the PAs’ layout in the TMA and determined the conservation gap and prioritization. We find that 43.92% of the high BCD areas and 84.39% of the medium BCD areas within the mountain area are inadequately protected, and 10.79% of the low BCD areas may be overprotected, classifying the above conservation gaps as three priority levels of conservation. Our study indicates that the current PAs in mountain areas are insufficiently protected and urgently need to be expanded; (2) by analyzing the coupling relationship between biodiversity and cultural diversity, it is found that only 23.90% of the relationships between the two were coordinated or above in the TMA; (3) we propose the optimization strategies of four typical conservation gaps in the TMA; (4) we finally develop an integrated conservation model of biological and cultural values for different PA categories in mountain areas based on a gap analysis. Optimizing mountain conservation and management based on the BCD evaluation results is conducive to promoting the sustainable development of human beings and nature while guaranteeing the unbiased allocation of conservation resources in mountain areas.