This paper investigates the relationship between the waveform area and fuel injection quantity. It is on developing on analysis method of waveform the effect of waveform area on fuel injection quantity of CRDI Diesel engine. The experimental methods using Pico oscilloscope and fuel injection tester are employed to measure current and voltage waveform and fuel injection quantity of solenoid injector. The one normal and two abnormal solenoid injectors are used. The experiment is carried out during no-load condition. A summary of the important results are as follows. 1) The area of the voltage and current waveform of the abnormal injector becomes larger than the that of normal injector, and the area of the current and voltage waveform is inversely proportional to the fuel injection quantity. 2) The area of the current waveform can be obtained more accurate results than that of voltage waveform. 3) It is possible to infer the fuel injection quantity by measuring the current waveform and calculating the area.