The invention provides a side-tracking slim hole layered fracturing string which comprises a sleeve, a first oil pipe, a tubing anchor, a fracturing plug and a tail string, wherein the first oil pipe, the tubing anchor, the fracturing plug and the tail string are arranged in the sleeve and are sequentially connected from top to bottom; the sleeve is provided with a flank hole; the upper end of the tail string is connected with the fracturing plug, and the lower end of the tail string passes through the flank hole; the tail string consists of a hanger, a second oil pipe, a ball seat, a third oil pipe, a soluble porous pipe, a fourth oil pipe and a tail pipe shoe which are sequentially connected from top to bottom; the hanger is connected with the fracturing plug. The invention also provides a fracturing method. A fracturing tool is not needed to be fed, not only can the large-displacement fracturing construction requirement be met, but also downhole tool feeding risks can be avoided, and meanwhile perforating operation at a lower reservoir stratum is omitted; compared with a well cementation sliding sleeve layered fracturing method, the risk that the sliding sleeve cannot be opened is avoided, furthermore, the side-tracking slim hole layered fracturing method has the characteristics that the blank of layered fracturing technology in feeding tail strings with an inner diameter of 76mm into a slim hole with an inner diameter of 118mm and cementing the well by using cement is filled.