A smaller screen of smartwatches compare to conventional mobile devices such as PDAs and smart-phones is one of the main factors that makes users to input texts difficult. However, several studies have only proposed a concept for entering texts for smartwatches without usability tests while other studies showed low text input performance. In this study, we proposed a new text entry method called Virtual Sliding QWERTY (VSQ) which utilizes a virtual qwerty-layout keyboard and a 'Tap-N-Drag' method to move the keyboard to the desired position. In addition, to verify VSQ we conducted a usability test with 20 participants for a combination of 5 key sizes and 4 CD-gains. As a result, VSQ achieved an average of 11.9 Words per Minute which was higher than previous studies. In particular, VSQ at 5 x 5 key size and 2x, or 3x CD-gain had the highest performance in terms of the quantitative and qualitative usability test.