The invention provides a remote online monitoring and optimizing method for the SCR efficiency of a diesel engine. The method comprises the steps of SCR efficiency measurement signal collection and signal monitoring and optimizing. According to the signal collection step, an ECU and a cloud end are connected through TBOX remote terminal equipment, and variable configuration is set at the cloud endand issued to a TBOX for measurement signal collection; data are uploaded to the cloud end, and data monitoring, analysis and optimization are conducted, wherein the data monitoring, analysis and optimization include the steps that 1), basic variables of the rotating speed, the oil amount, the torque, the vehicle speed, the environment temperature, the water temperature, the air inflow and the SCR efficiency real-time value are continuously recorded and stored, an SCR efficiency measured value graph is output in real time for online monitoring, and meanwhile SCR efficiency cloud data are usedfor feedback of calibration of an optimization rack; and 2), SCR efficiency diagnosis variables including the SCR temperature, the SCR upstream NOx value, the SCR downstream NOx value, the upstream and downstream NOx release state, the exhaust gas flow, the urea injection amount, the NH3 storage value, the engine running mode, the SCR efficiency measured value and the SCR efficiency limiting value are continuously recorded and stored, and after the SCR efficiency diagnosis enabling condition is met, a robustness graph is automatically output.