Skull-base chordoma (SBC) is a rare, aggressive bone cancer with a high recurrent rate. Genomic studies of SBC have improved our understanding of the disease’s biology. However, the molecular biological characteristics and the effective therapy of SBC remain unknown. Here, we carried out an integrative genomics, transcriptomics, proteomics, and phosphoproteomics analysis of 187 skull-base chordoma tumors. We identified chromosome instability (CIN) as a prognostic predictor and a potential therapeutic target in SBCs. Multi-omic data revealed downstream effects of CIN, in which, RPRD1B served as a putative therapeutic target for radiotherapy resistant SBC patients. Chromosome 1q gain was significantly enriched in CIN+ SBCs, and associated with upregulated mitochondrial functions, which led to inferior clinical outcomes. Immune subtyping identified an immune cold SBC subtype with CIN+ feature, and elucidated an association between losses of chromosome 9p/10q and immune evasion. In addition, proteomics-based classification of SBCs revealed that P-II and P-III subtype tumors had both CIN+ and immune cold features; however, P-II tumors with apoptosis suppression features were more invasive. These identified molecular features of CIN were further confirmed in 17 pairwise SBC patients. Our observations and the multi-omic data resources might guide research into the biology and treatment of SBC.