Precambrian granitoid rocks are widely distributed in northern Guangxi. According to rock associations, these granitoid rocks can be grouped into two types, i. e., graniodioritic rocks and biotite granitic rocks. The A/NKC values of both types of rocks are higher than 1.10, and hence they can both be assigned to aluminum over_saturation rocks. However, geochemical differences between the two types of rocks are also quite obvious. Compared with the biotite granitic rocks , the granodioritic rocks are relatively poor in silica and potassium and enriched in iron and magnesium, and have lower rubidium abundance and higher strontium and barium content. As for REE content, the granodioritic rocks have higherΣREE values and higher LREE/HREE ratios, whereas the biotite granitic rocks display quite clear negative europium anomalies. The variation ranges ofεNd(T) values of the two types of granitoid rocks are similar to those of the basement rocks (Sibao Group), but theεNd(T) values of granodioritic rocks are more close to those of the metamorphic mafic -ultramafic rocks of the Sibao Group, and the biotite granitic rocks are close to the metasedimentary rocks of the Sibao Group in this aspect. Based on a comprehensive analysis of their tectonic setting, it is concluded that the two types of granitoid rocks were formed at different stages of the collision between the Cathaysia block and the Yangtze block, and were produced by partial melting of the Sibao Group with different maturities at different depths.