Spiral grain selector is a very important part of manufacturing process of single crystal blade, which is the key component of the aero-engine and industry gas turbine. Finite element simulation and experiments are used for researching the temperature effect of spiral grain selector, the grain structure and grain growth in the directional solidification process of DD6 superalloy. The results show that simulation method can well predict the temperature change of directional solidification process, and the grain microstructure simulation is similar to the competitive growth of grain according to the experimental samples. Because the location of the grain is replaced, whose orientation is different from the direction of temperature gradient, the mean radius of grain increases with increasing height in the starter block, while the grain density declines. The simulation results of grain morphology in the spiral part are consistent with experimental pictures from the EBSD orientation mapping technology. The grain is more advantage to grow in the spiral part, which is located in the interior and upper part of the spiral channel longitudinal section.