The invention relates to a casing differential-free dragging fracturing technology and a fracturing tool string and belongs to the field of oil-well underground operation. According to the invention, the steps of positioning in well, sealing, jetting holes, fracturing, circularly backwashing and unsealing pipe columns are adopted for performing multistage staged fracturing on unconventional hydrocarbon reservoirs, such as tight gas reservoirs and shale gas reservoirs, so that the problems that the present multistage staged fracturing technology is complex in process, a compression packer is drilled after the fracturing operation is completed, the process consumes long time, the cost is high and the stratum is easily polluted can be solved. The casing differential-free dragging fracturing technology can effectively reduce the construction energy consumption, has the advantages of no differential limitation, no limitation to fracturing layer interval, no requirement for drilling and shorter construction time and has positive popularizing significance in performing multistage staged fracturing on the unconventional hydrocarbon reservoirs, such as tight gas reservoirs and shale gas reservoirs.