Alternating current field measurement (ACFM) has become a promising non-destructive testing technique in ILI. The minimum crack detected by ACFM now available is 3 mm in length. By now ACFM has not yet been used in ILI of pipelines. ACFM inducer for ILI of pipelines is designed by means of numerical simulation in this paper, attempting to bring ACFM to use in ILI of pipelines. The numerical simulation model of the inducer is built to evaluate the magnetic field perturbation of a surface-breaking crack on the inner surface of the pipeline for the purpose of enhanced crack detection. Model predictions show good agreement with experimental data, verifying the accuracy of the model. The model includes the influence of various parameters, such as core material, core dimensions, core positions, and magnetic sensor position, on the perturbed magnetic field above a crack. Optimized design parameters for the ACFM inducer for ILI of pipelines are given according to the analysis results, which provide for a greatly improved detection effect.