This chapter reviews the significant development of research on the second language acquisition of the sound system of standard Chinese. While major findings from studies on both segmental (vowels and consonants) and supra-segmental features of L2 Chinese phonology are outlined, particular attention is paid to the acquisition of Chinese lexical tones. This review begins with a summary of how non-native tonal errors have historically been viewed and how these views have changed over time. Several aspects of the second language Chinese tone studies are reviewed and discussed, such as the acquisition order of tones, the third tone and its sandhi rules, tone perception and production, positional effects in second language tone grammar and the acquisition of Chinese intonation, etc., followed by a discussion regarding research approaches of empirical studies of the second language perception and production of Chinese tones. The chapter ends with pedagogical implications and points out future directions of research on second language Chinese sounds.