Natural gas hydrate muddy siltstone reservoirs are characterized by weak cementation and low strength. Hydrate decomposition reduces the strength of the reservoir and the width of the seepage channel decreases or even closes. The “double-added” reforming slurry is a type of slurry that can enhance the strength and permeability of the reservoir after curing， but the rheological properties of the double-added slurry differ greatly from those of the fracturing fluids and it does not contain sand， and the influence mechanism of the construction parameters of slurry splitting on the expansion of the slurry in the shot-hole clusters is not clear yet. In this paper， a two-dimensional hydrate reservoir fracturing grouting numerical simulation model is established based on the extended finite element method to study the influence of shot hole parameters and fracturing mode on fracture expansion. The results show that： the stress field induced by the cluster spacing of injection holes has a greater influence on the fracture extension when the cluster spacing of injection holes is small， and the slurry extension becomes obvious， and with the increase of the cluster spacing of injection holes， the stress interference between clusters decreases gradually， and the original geostress plays a main role in the direction of the slurry extension； the more the number of injection holes under the same cluster spacing， the stronger the stress interference between clusters is， and the smaller the cluster spacing of injection holes is； the distance of the slurry extension under the synchronous splitting mode is not uniform， and the sequence splitting and intersecting splitting modes are not uniform， and the distance of slurry extension under the simultaneous splitting mode is not uniform. In synchronized fracturing mode， the distance of slurry expansion is not uniform， and when fracturing in sequence and alternating fracturing， the previously formed cracks will be gradually squeezed， and the width of the cracks will gradually become smaller， which increases the fracturing pressure of the subsequent shot hole clusters， and is not conducive to the fracturing of the reservoir. The results of the study provide a reference basis for the design of fracture grouting in natural gas hydrate reservoirs.