However, several investigations proved clearly that in the high-cycle regime, a decrease of fatigue strength with an increased number of cycles still occurred, even if corrosion or temperature effects were excluded. Therefore, the fatigue design of components submitted to loadings below the knee point of the S-N curve must consider this fact to avoid failures. Concerning the course of the S-N curve in the very high-cycle area, he gave material and manufacturing dependent recommendations. [PERSON] et al. [17] developed a hybrid (the combination of micromechanics and tests) and multi-scale (damage in micro-scale linked to macroscale fatigue properties) method of predicting the S-N curve for every point in a short fiber composite. This proposed method was-based not only on tests but on a combination of manufacturing simulation, tests, and multi-scale mechanics. An extensive test program was undertaken to study the fatigue behavior of short fiber composites and validate the concept of the Master SN curve (MSNC) approach. The MSNC approach was compared with two commonly used approaches: strength-based scaling and the test-based interpolation. The results of the MSNC approach are in good agreement with the experimental results, and the MSNC approach was confirmed to be more accurate than the prevalent methods. [PERSON] [18] generalized the concept of \"crack-like\" notches to finite life, according to Critical Distance Method, found that the S-N curves of all notches were very close to the SN curves for cracked jaws up to a certain number of cyclic N, and suggested new simple estimates for SN curves of notches. However, there are few systematic studies on fatigue SN curve of high strength steel wire used for bridge cables. It can be seen that most experimental studies tend to summarize experimental phenomena, but fail to establish quantitative and systematic fatigue S-N curves for reference by other researchers. Moreover, the corrosion fatigue properties of intact steel wire are generally studied, and the properties of corroded steel wire or steel wire with initial defects are rarely considered. However, for old steel wire that has been in use for many years, some defects appear on the surface of the steel wire due to environmental erosion. A large number of studies have proved that the corrosion of the steel wire surface under chlorine salt erosion is dominated by unilateral corrosion and pit corrosion [19]. Under the chlorine salt environment, the destruction of passivation membrane by reactive ion Cl' does not happen evenly across the whole metal surface; it happens locally first. That is to say, the destruction of the passivation film occurs only in an individual point or in a small area. This area, where the iron matrix is exposed, forms a potential difference with other areas. The iron matrix in this small area acts like a micro anode and is surrounded by the cathode formed by a large area of passivation film, thus forming a micro anode- macro cathode corrosion battery and accelerating the formation of local pitting pits. The morphology of corrosion pitting on the surface of corroded old steel wire can be abstracted into four shapes: semi-ellipsoidal shape, honeycomb shape, groove shape and saddle shape [20]. To simplify the electrochemical process of corrosion pit formation, a machine-cut notch is used to represent an erosion pit caused by a corrosive medium firstly. In addition, then, a new type of test device is designed to perform the synchronous pulsating fatigue loading on multiple wires and shorten the duration of fatigue tests. Subsequently, a series of S-N curves of steel wire with initial defects under different stress ranges and corrosive medium with different concentrations and pH values can be obtained. Finally, the effects of the concentration and pH value of corrosive solution, and the shape and dimension of initial defect on fatigue corrosion performance are investigated.