This paper examines the motivation for consonant gemination in Japanese loanword by analyzing NTT database series Nihongo-no Goitokusei (Lexical properties of Japanese). Based on the comprehensive investigation, it is pointed out that consonant gemination is a result of a phonological augmentation in prominent position, that is, accented syllable.and word medial position. And it is argued that the gemination in word-medial position is due to the influence of phonological augmentation and accentuation assigned by pseudo-morphemic suffixes ― /-ikku/ (-ic), /resu/ (-less), /-mento/ (-ment). /-aa/ (-er, -or), /-shon/ (-tion, -sion) and /-ingu/ (-ing).