AbstractIn this paper, the cylindrical structures phase aggregation behavior of the blend materials is explored experimentally. The phase aggregation behavior is a phenomenon in which the cylinder phase aggregates nearby, which occurs after phase separation. With mixing the polystyrene‐b‐polycarbonate with polystyrene, a cylindrical state is first obtained, and then such state is changed to a larger cylinder state. It is found that such state aggregation behavior is the function of annealing time and temperature, while the maximum temperature is less than the molten temperature. First, a cylindrical state with 11–14 nm diameter is obtained, with a 3 nm standard deviation. Then the neighboring cylinders move to aggregate together and the cylinder diameter is enlarged quickly to ≈30 nm and above, with a higher standard deviation. It is also found that the aggregation behavior is consistent over a wide temperature range from 150 to 200 °C. For the blend material used, when cylinder is formed, the free energy of the system is not stable. Then, keeping the annealing temperature constant and the annealing time increasing, the neighboring cylinders aggregate and form large‐diameter cylinders. This dynamic behavior opens a new window of self‐assembly applications by obtaining different structures through process control.