The invention discloses a diesel engine transient-emission control system based on an intelligent transportation system and a control method of the diesel engine transient-emission control system, and belongs to the technical field of diesel engine transient-emission control. The control system is characterized in that an engine sensor information acquisition unit and an intelligent transportation system information acquisition and transient operating condition prejudgment unit are connected with an intake/exhaust control actuator electric control unit; and the intake/exhaust control actuator electric control unit is connected with an electric control EGR (Exhaust Gas Recirculation) valve, a throttle valve, a VGT (Variable Geometry Turbocharger) and an urea injector. According to the invention, the vehicle-mounted intelligent transportation system is used to acquire such information as traffic flow, road length and traffic light ahead; and based on certain driving optimization and intelligent driving strategies, transient operating conditions can be predicted in advance to guide the transient-emission control system to make a response in advance, so that the diesel engine transient-emission control efficiency can be greatly improved.