Published version of an article in the journal: Mathematical Problems in Engineering. Also available from the publisher at: http://dx.doi.org/10.1155/2014/549790 ; The traditional mechanical instrument lacks the ability to satisfy the market with characters of favorable compatibility, easy upgrading, and fashion. Thus the design of a TFT-LCD (thin film transistor-liquid crystal display) based automobile instrument is carried out. With a 7-inch TFT-LCD and the 32-bit microcontroller MB91F599, the instrument could process various information generated by other electronic control units (ECUs) of a vehicle and display valuable driving parameters on the 7-inch TFT-LCD. The function of aided parking is also provided by the instrument. Basic principles to be obeyed in circuits designing under on-board environment are first pointed out. Then the paper analyzes the signals processed in the automobile instrument and gives an introduction to the sampling circuits and interfaces related to these signals. Following this is the functional categorizing of the circuit modules, such as video buffer circuit, CAN bus interface circuit, and TFT-LCD drive circuit. Additionally, the external EEPROM stores information of the vehicle for history data query, and the external FLASH enables the display of high quality figures. On the whole, the accomplished automobile instrument meets the requirements of automobile instrument markets with its characters of low cost, favorable compatibility, friendly interfaces, and easy upgrading. © 2014 Yunsong Xu et al.