Located in southwestern Guizhou Province, the Nibao gold deposit discovered recently is an important Carlin-type gold deposit. Pyrite is the major gold-bearing mineral in the deposit. Petrographic observations and electron microprobe analysis (EPMA) of sulfides from the Nibao gold deposit show that arsenic pyrites is the major gold-bearing mineral. A combined detailed field work, ore petrographic investigation and EPMA studies revealed three kinds of arsenic pyrites, i.e., zoned arsenic pyrite (PyⅠ), colloidal arsenic pyrite (PyⅡ), and bioclastic arsenic pyrite (PyⅢ). The EPMA and LA-ICP-MS analyses indicate that PyⅠ is mainly composed of pyrite core and arsenic pyrite zones, formed in different metallogenic stages. Pyrite core is characterized by high S, Fe concentrations and low Au, As, Ag and Cu, indicating a sedimentary-diagenetic origin or precipitation in the early metallogenic stage. Zoned arsenic pyrite, growing along pyrite core, is characterized by high Au, As, Ag, and Cu concentrations, indicating a main mineralization hydrothermal origin. The colloidal and bioclastic arsenic pyrites with homogeneous texture are similar to the rims of zoned pyrite with characteristics of high Au, As, Ag, Cu and low S, Fe, indicating that PyⅡ and PyⅢ were probably formed synchronously with the arsenic pyrite zones of PyⅠ. Arsenopyrite mainly occurs as overgrowths on arsenic pyrite and has rich As and poor Au, Ag, and Cu concentrations, suggesting that arsenopyrite was probably formed in the post-mineralization stage. The precipitation order of gold-bearing sulfides is as follows:As-poor sedimentary pyrites or early metallogenic stage pyrites→arsenic pyrites→arsenopyrite. Textures, paragenesis and trace element geochemistry of pyrite indicate that As-poor pyrite core mainly deposited during sedimentation, while most of economic metals (Au, Ag, As, and Cu) were introduced through the Late Yanshanian subsequent hydrothermal superimposition. The compositions of the gold-bearing pyrites support a magmatic hydrothermal model for the origin of gold-sulfide mineralization.