Based on the method of reconstructing dynamic phase space, this paper calculates the fractal dimension,Lyaponove index and complexity of the resistivity data gained from several stations around Tangshan area before and after the Tangshan earthquake and from Shandan station in 1990. The results show that the time sequence of ground resistivity is of fractal dimension structure,and under normal condition its attractor's dimension is about 2.5. The calculation of its complexity suggests that the change of ground resistivity is far more complicated than other standard attractors.