The two-layered perovskite manganites La_1.34Sr1.66Mn2 - x_CrxO₇ ( x = 0,0.1,0.3,0.4) were prepared by a standard solidstate reaction method. The XRD patterns indicate that all samples can be indexed to a tetragonal Sr₃Ti₂O₇ type sturcture with a space group I4/ mmm. The cell volume V of the samples decreases monotonically with increasing Cr^{3 +} concent ration. For lightly Cr^{3 +} doped sample ( x = 0. 1), the three-dimensional long-range ordering ferromagnetic transition temperature T^3Dc increases,while the two-dimensional short-range ordering ferromagnetic transition temperature T_c^2D decreases. A minimum of the c parameter,a maximum of the a parameters and a minimum of the c/ a ratio were found in the x = 0.1 sample. The change of the double-exchange-interaction resulting from the serious lattice distortion is the main cause of the variation of the magnetic orderingt ransition temperatures in this sample. For the heavily Cr^{3 +} doped samples ( x = 0.3, and 0.4), T_c^3D decreases,but T_c^2D almost remains stable. The resistivity increases with decreasing temperature in the range of 150～300 K, showing a insulating or semiconductor behaviour. The resistivity increases monotonically with increasing Cr^{3 +} doping level.