The data on-site is transmitted to the control and protection systems by redundant configured measurement bus in Yunnan – Guangdong ±800kV DC transmission project, to achieve the stable operation of the UHVDC system. This paper describes the configuration,fault identification and switching logic of measurement bus.Based on the problem occurred during operation,pointing out the defect of design in fault identification.At last, improvement proposal is given,and the proposal has been applied in yunnan-guangdong UHVDC system on site.