The purpose of the present study is to investigate frequency related information and syllable structure constraints on Sino-Korean. Previous studies on Sino-Korean have mostly investigated the historical change of sounds and reviewed archaic features of Chinese language in Sino-Korean. Unfortunately, there is little study on the sounds of contemporary Sino-Korean in terms of syllable structure constraints. For the purpose of the present study, sounds of 7,742 Chinese characters used in Sino-Korean (7,795 syllables) were investigated and syllable matrices made based on the results of frequency related information. As a result, 483 syllable types were observed and the most frequently observed syllables were as follows: /ku/ (103) > /ki/ (100) > /ju/ (87) > /pi/ (86). Only 16 out of 19 consonants are used for Sino-Korean. /$t^{ast}$/ and /$p^{ast}$/ are never used in Sino-Korean and /kh, $s^{ast}$, $k^{ast}$/ occur only a few times (3, 2, 1 respectively). /k/ (17.5%) shows the highest frequency and /n, ${eta}$, 1, tc, m/ occupied the next rankings. Among 20 vowel types, /a/ showed the highest frequency and /o, u, i, $j{Lambda}$, ${Lambda}$/ occupied the next rankings. Based on the syllable matrices, gaps were observed and classified into accidental or systematic ones. Onset and nucleus, nucleus and coda, onset and coda, and other syllable structure constraints of Sino-Korean were listed.