Toroidal surfaces have wide applications in optics and manufacturing industry. Due to the strong aspherical surface profile of a toroidal surface, there are few optical measurement techniques proposed or reported for its measurement. This paper proposed digital Shack Hartmann wavefront sensor (SHWS) with extendable dynamic range. Instead of the traditional spherical lenslet array, which cannot sample the wavefront in two directions simultaneously, an elliptical lenslet array realized by a spatial light modulator (SLM), which provides different optical powers in two directions, is used in the system. With the incorporation of the extended version of the traditional SHWS, the reference-free wavefront sensor (RFWS), curvature matrix is measured, which can be further reconstructed into the surface profile. Both numerical simulation and experimental study has been conducted and the feasibility of measuring toroidal surfaces in the RFWS system with an elliptical lenslet array is proven.