This paper presents an approach for the detection and analysis of micro-scratch detected on the surface of steel cord (steel filament) using eddy current sensor (ECS). This work aims to point out and eliminate the defective products and containing surface defect in wet drawing process. In other words, a quality gate was established to prevent sending defective goods to customer. During wet drawing process, steel filaments were manufactured by drawing process through multi-dies system ranging from bigger diameter called brassed wire to smaller diameter called filament. An eddy current sensor was used to generate a high-frequency magnetic field around the sensor coil where the filament went through at the output end. The test coil was centered inline of wire path and connected to pre-amplifier then send the signal to instrument which was used to set working conditions for the experiment. If a defect appears when filament passes through the test coil, the eddy current will appear and sensor will send the signal to stop the wet drawing process. The artificial defect was created on a sample and the amplitude of those defects were measured to set the threshold. The amplitude signal of artificial defect was about 10% corresponding to specification of crack’s depth of 20 micrometers. The production was carried out with applied setting condition under inspection of eddy current sensor. we produced 182 products x 38,000m, the defective ratio was 26.37%. There were two typical types of defect: the longitudinal scratches and the hole defect which containing an additional particle. In future works, the surface scratches will be collected, and then analyzed two positions including inside and outside of defect area in order to identify the atomic ingredients to identify the origin of the defects.