Oral squamous cell carcinoma (OSCC) is the most common malignant tumor of the oral and maxillofacial region. Due to its unique location, earlier and more accurate diagnosis and more minimally invasive treatment of OSCC is of major importance. Herein, gadolinium-containing semiconductor polymer nanoparticles (SPN-Gd) were designed and prepared. The nanoparticles consist of a near-infrared (NIR) absorption semiconductor polymer (PCPDTBT) served as fluorescence signal source and a photothermal conversion agent (PTA) and a gadolinium-grafted triblock amphiphilic copolymer (F127-DTPA-Gd) served as a magnetic resonance imaging (MRI) contrast agent and nanocarrier. The experiments in vivo showed that SPN-Gd could act as an MRI contrast agent and optical image agent with a long retention time, and it had a significant inhibiting effect on tumors of OSCC mice model through photothermal therapy (PTT). Thus our study provides a simple nanotheranostic platform composed of two components for efficient MR/fluorescence dual-modal imaging-guided PTT.