According to the activation of the fashion electronic commerce, this research investigated the merits and demerits and improvement plan of the 3D virtual try-on technology using the qualitative research method. This research was performed by interview with 70 evaluation group. The evaluation group of 3D virtual try-on was organized and the fit evaluation process by 3D human body scan and the 3D virtual try-on of the i-Fashion technology center were experienced. This study was performed by interview after the actual and virtual try-on about the casual shirt. The convenience and accuracy of measurement, usability in online shopping, body evaluation, complement of sizing system, and body shape management were discovered as merits. The requirement of high accuracy in sizing and avatar, limits of fabric expression, practical limitation by cost, vexatious of measurement garment, differences between real and virtual fittings, personal information leakage risk, and etc were pointed out as demerits. The mass customization, customized garment connected with medical service, humanized avatar, improved fitting report, entertainment, coordination, wardrobe manager were proposed as improvement plan.