Improving the utilization efficiency of Al-based metallic fuels and enhancing the energy output performance of composite explosives constitute a crucial research direction in the field of energetic materials. To explore the effects of Al-Li alloys on the safety and energy output characteristics of composite explosives， systematic investigations on the mechanical sensitivity， explosion heat， and underwater explosion performance of three composite explosives （E_Al， E_Al-2.3Li， and E_Al-5Li） containing pure Al， Al-2.3Li alloy， and Al-5Li alloy were carried out via the Langley D-optimization method， explosion heat tests， and underwater explosion experiments.The results show that under the condition of 50% ignition probability， compared with the EAl explosive， the impact energies of E_Al-2.3Li and E_Al-5Li are reduced by 33.02% and 42.36%， and their friction loads are decreased by 19.73% and 32.88%， respectively. The addition of Al-Li alloys increases the mechanical sensitivity of composite explosives， and the sensitivity to mechanical stimuli is further aggravated with the increase of Li content. In terms of explosion heat， Al-Li alloys can significantly improve the explosion heat of composite explosives. Among all formulations， E_Al-2.3Li exhibits the maximum explosion heat of 8.712 MJ·kg^-1， which is approximately 6.3% higher than that of E_Al. In the underwater explosion tests， the total energy of E_Al-2.3Li and E_Al-5Li reaches 7.177 MJ·kg^-1 and 6.954 MJ·kg^-1， increased by 8.33% and 4.97% compared with E_Al， which indicates that the incorporation of Al-Li alloys can effectively enhance the underwater energy release capacity of explosives.Comprehensive analysis demonstrates that the introduction of an appropriate amount of Li can effectively improve the comprehensive energy output performance of explosives， whereas the Li content has an optimal range. The E_Al-2.3Li explosive achieves an excellent balance between safety and energy output performance， presenting superior comprehensive properties. This study reveals the regulation law of Li content in Al-Li alloys on the safety performance and energy release characteristics of composite explosives， and provides theoretical basis and experimental references for the optimal design and engineering application of reactive metal fuels in high-energy metal-based explosives.