Judging from their contrubutions as historical materials, both Xin Tang Shu (新唐書 ) and Jiu Tang Shu (舊唐書 ) have their respective merits and demerits. It is unwise to prejudice against one or the other.Jiu Tang Shu (舊唐 書 )was completed in the age of chaos and turmoil of the Five Dynasties (五代 ).It happened to reserve more primary historical meterials than its kind. However, one must bear in mind that from generation to generation, a number of errors may have crept into and scattered over the whole books. Xin Tang Shu (新 唐書 ) is complementary to Jiu Tang Shu (舊唐書 ). Its most important contrubution is its inclusion of Biao (表 ) and Zhi (志 ). Its major pitfall lies in the simplicity of its text. Many uesjul historical materials were omitted. Furthermore, its record is too vague and inaccurate so far as the concept of figure is concerned. In conclusion, the Xin Tang Shu (新唐書 )and Jin Tang Shu (舊唐書 ) have their respective credits and defects. We should not treat or accept them indiscriminately.