Safety applications of intelligent connected vehicles are trigged by V2X (vehicle to everything) messages. Therefore, corresponding application test should be done under a V2X full coverage condition. However, the reality of low V2X penetration makes on-road test difficult. To support V2X road test, a roadside live broadcasting system, which simulate V2X un-equipped road vehicle information via V2X array node, is designed. Roadside Lidars are used to collect on-road vehicles' information, while road scenario extraction and V2X based scenario re-construction procedures are described. To improve the simulation accuracy, a pipe-line based forecasting algorithm is proposed. Moreover, a criticality-based scenario extraction method is designed to generate DT (digital twin) scenario library, which could be used to support closed field test. Corresponding test procedures are given.