Mining functional genes associated with panicle yield-related traits represents an important avenue for genetic improvement and molecular breeding of foxtail millet. In this study, a genome-wide association analysis was conducted to identify a locus associated with panicle weight on chromosome 3 of foxtail millet. Combined with linkage disequilibrium analysis and genome annotation, SiNAC075 (Seita.3G111000) was identified as the candidate gene. The gene spans approximately 3.3 kb and contains 4 exons and 3 introns, as well as UTRs. Haplotype analysis indicates that key variation of SiNAC075 resides in the promoter, with H001 as the elite haplotype and H005 as the inferior haplotype. Phylogenetic analysis showed that SiNAC075 shares the closest genetic distance with Sevir.3G113300, and the two proteins cluster in the same clade of the phylogenetic tree. Expression profiling across the whole growth period revealed that SiNAC075 is predominantly expressed in roots at seedling and heading stages, as well as in flag leaves at flowering stage. Furthermore, as a transcription factor, SiNAC075 possesses a typical nuclear localization signal. Additionally, leveraging the key variations in the promoter, we developed a KASP marker to identify the elite allele H001 and inferior haplotype H005, thereby providing technical support for improving yield breeding efficiency in foxtail millet.