The standard language of Chinese is referred to as putonghua 普通話 ‘common speech’ in mainland China, guoyu 國語 ‘national language’ in Taiwan. The phonology of these two standard languages is based on the phonology of the Beijing dialect. Although these two are mutually intelligible, there still exists discrepancies in phonology, lexicon, syntax, and so forth. In order to examine the different standard reading pronunciations of characters, this paper compares “Putonghua yiduci shenyin biao” 普通話異讀詞審音表 (1985) of mainland China and “Guoyu yi zi duoyin shending biao” 國語一字多音審訂表 (1999) of Taiwan. It is confirmed that over 200 standard reading pronunciations show discrepancies. This paper also tries to explain the causes of different standard reading pronunciations. The results of study indicate that putonghua tends to employ “irregular” pronunciations caused by exceptional development such as analogical reading based on the graphs, popular pronunciations, etc., while guoyu shows a tendency to follow “regular” pronunciations based on the categorization of traditional rhyme books. Moreover, there are cases that the two norms adopt different reading pronunciations from a) distinct chronological layers, or b)different pronunciations of polyphonic characters. In addition, guoyu tends to keep multiple pronunciations where they make semantic distinction, whereas putonghua adhere to the “one character, one sound” rule. In cases that the discrepancy was caused by different chronological layers or popular pronunciations, contrary to the former, guoyu tends to admit one pronunciation, while putonghua allows multiple pronunciations.