When slurry support pressure is large excessively during slurry shield tunneling at soft aquifer, hydraulic fracturing may occur causing collapse of excavation face. It is significant to investigate related influence factors of fracturing pressure to prevent occurrence of hydraulic fracturing in slurry shield. Considering the high challenge and safety risk in field test, a laboratory hydraulic fracturing apparatus was designed and blind hole samples were adopted to simulate fracturing during slurry shield tunnelling. Artificial clay with different strength was prepared by orthogonal test and it was used to study the relationship between fracturing pressure and soil unconfined compressive strength. Besides, slurry with different viscosity was adopted to conduct fracturing tests on blind hole sample, in which the effect of slurry viscosity on fracturing pressure was investigated. Test results show that fracturing pressure increases linearly with increase in unconfined compressive strength. When unconfined compressive strength is the same, the greater confining pressure is, the greater fracturing pressure will be, and the increment of fracturing pressure at each strength is basically equal to the increment of confining pressure. When slurry viscosity is less than 27s, fracturing pressure increases with increas in slurry viscosity at a decreasing rate. When slurry viscosity is greater than 27s, fracturing pressure almost stabilizes and hardly grows any more. There is obvious fracturing surface when the sample is fractured. Under different slurry viscosity, fracturing surfaces are basically the same, extending obliquely from the bottom of center hole, indicating that the failure mode of blind hole sample is not affected by slurry viscosity.