As one of the basic human interface devices, the keyboard has a versatile application in many fields. To standard keyboard, the commonly used Qwerty keyboard layout is not designed for improving work efficiency. The keyboard entry is a complicated human engineering problem, which varies with the factors such as typists' habits, usability divergence of fingers and different text information. By decomposing the keyboard entry process, assuming parameters about fingers and analyzing text information, the paper defines the Distance Matrix and the Text Matrix to build a more objective model for the layout comparison and optimal design of the standard keyboard. Comparison of the existent keyboard layouts is made and a new efficient layout for inputting Pinyin-based Chinese is established.