$CaTiO_3-x(La_{1/3}Nd_{1/3}TiO_3;(0le extrm xle0.8)$ system was prepared by reaction of $CaCO_3,;LaO_3,;Nd_2CO_3$ and ,TEX>$TiO_2$</TEX> mixture at 1673 K, which can be applied for microwave dielectric ceramic materials. The lattice parameters of(1-x))$CaTiO_3-x(La_{1/3}Nd_{1/3}TiO_3;(0le extrm xle0.8)$ system increased with the increase of x. Its structure was investigated by Rietveld profile-analysis of XRD in detail. Cations $ La^{3+}$ and Nd^{3+}$ were located at the $Ca^{2+}$ site in the range of $0le extrm xle0.8$. crystal structure in $;(0le extrm xle0.6)$ maintained space group Pnma with CaTiO_3 structure. The tiled and distorted $TiO_6$ was gradually released with the increase of x in $0le extrm xle0.6$ .The structure was changed to a new space group of $Pmn2_1$ at the x value of 0.8. The relative dielectric constant $(epsilon_r)$ of $(1-x)CaTiO_3-x(La_{1/3} Nd_{1/3})TiO_3$ ($(0le extrm xle0.8)$) system was exponentially decreased by with the increased of x. The temperature coefficient of resonant frequency $( au_f)$ decreased with the increase of x in $0le extrm xle0.6$ and then increased again at x=0.8 due to the change of crystal structure. The value of Q$cdot f_o$ was 13800 (GHz) at x=0.2 and was very low under 2000 (GHz) in 0.4$leq$x$leq$0.8.