Abstract: With the rapid development of China's economy, the country has put forward higher requirements for energy conservation, emission reduction, and low-carbon environmental protection. Engineering experience has shown that the slenderness ratio has a significant impact on the load-bearing performance of slender load-bearing components. For the purpose of economy and energy conservation, concepts such as the ultimate pull-out force per unit volume and the optimal slenderness ratio were proposed. A calculation and analysis model for the fully grouted anchorage system was established using PFC software. The influence of slenderness ratio on the pull-out performance of the fully grouted anchorage system was systematically studied from the changes in anchorage length and anchorage width dimensions. Research has shown that: （ⅰ）The slenderness ratio directly affects the pull-out performance of the fully grouted anchorage system; （ⅱ）For a fully grouted anchorage system under specific conditions, there exists an optimal slenderness ratio that can achieve the goal of using the least amount of material to maximize bearing capacity; （ⅲ）The research conclusion on the influence of slenderness ratio on the pull-out performance of the fully grouted anchorage system under two-dimensional models is also applicable to three-dimensional models or real working conditions.