The invention relates to the technical field of through casting coring of an oil field production well, in particular to a through casting side wall penetrating coring tool. The Through casting side wall penetrating coring tool comprises a radial horizontal drilling guide mechanism, and further comprises a casing windowing mechanism and a coring mechanism. The radial horizontal drilling guide mechanism comprises a hydraulic anchor and a guider, the lower end of the hydraulic anchor is connected with the guider through an upper connector, a sealing base is designed on the inner wall of the upper connector, and a sidewall contact device and a straightening mechanism are arranged on the side wall of the lower end of the guider. The through casting side wall penetrating coring tool can penetrate through a casting for coring work of orientating and deep penetrating, coring construction is easy, convenient, low in cost, safe and reliable, the adaptability to the stratum is high, and the coring yield rate is high. Taken rock cores are regular, lithology and oiliness observation can be visually carried out, lithology, electrical property, physical property and oiliness analysis and tests can be carried out with the help of instruments, the porosity, the permeability and other reservoir parameters are obtained, and the tool has direct guiding significance on reservoir assessment.