In order to research the influence of rolling direction on the quality of cold-rolled magnesium alloy sheet for car lightweight, the microstructure and mechanical properties of eight-pass cold-rolled Mg-3.5Zn-0.8Ca magnesium alloy sheet in different rolling directions after annealing at 380 ℃ were analyzed by optical microscope, EBSD method and tensile mechanics experiment. The results show that after cold rolling of Mg-3.5Zn-0.8Ca alloy, the twin crystals are formed in thin plate, and the RD cold rolled sheet generates the most twin phases. The grain size in the microstructure can be refined when the annealing is at 380 ℃ for 1.5 h, the grain size is almost 20 μm in each rolling direction, and the structure has been transformed into recrystallized structure. At the same time, many grains have grown up, and the yield strength of sample in the RD direction is higher than that in the TD direction. Thus, the annealed sheet metal obtained by the one-way rolling reaches the maximum yield strength in the rolling direction, and the annealed sheet metal perpendicular to the rolling direction reaches the lowest yield strength.