Abstract
Stock movement prediction remains a central challenge in financial machine learning due to the inherent noise, non-stationarity, and multi-source heterogeneity of market data. While recent approaches leveraging graph neural networks (GNNs) have achieved promising results by modeling relational structures among financial assets, most existing methods treat stocks as homogeneous nodes and rely on a single data modality. In this paper, we propose HeMoG (Heterogeneous Multi-Modal Graph Learning), a novel framework that constructs a heterogeneous stock graph incorporating price correlations, sectoral hierarchies, and macroeconomic factor linkages, and fuses these with multi-modal signals (numerical time series, textual news, and social media sentiment) through a cross-attention fusion mechanism. To address the challenge of learning discriminative stock representations under noisy labels, we introduce a Hierarchical Contrastive Loss (HCL) that operates at three levels: node-level stock embedding, sector-level prototype, and market-level global distribution. Extensive experiments conducted on three benchmark datasets (S&P 500, NASDAQ-100, and CSI-300) demonstrate that HeMoG outperforms ten competitive baseline models, including state-of-the-art approaches such as S3G (ICASSP 2026), achieving an average improvement of 4.7% in directional accuracy and 8.3% in Matthews Correlation Coefficient (MCC) across all datasets. Ablation studies confirm the significant contributions of both the heterogeneous graph structure and the hierarchical contrastive loss to model performance.
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