We show that any integral Brakke flow coming out of a rotationally symmetric double cone with entropy at most two must stay rotationally symmetric for all time, provided the flow is smooth for a short time. We also show the existence of a non-self-similar flow coming out of a double cone with entropy at most two, and give an example of such a flow with a finite time singularity.Corollary 1.3. Suppose C is of the form (1.2) and has entropy λ[C] < 2. Suppose M is an integral, unit-regular and cyclic Brakke flow coming out of C. If M is smooth on (0, T ), then M is rotationally symmetric across the x 1 -axis. The only possible singularity model of M is the round cylinder R × S n−1 . Moreover, there can be at most one of such singularity, which, if it exists, must occur at the origin.We can also apply Theorem 1.1 to cones with O(p + 1) × O(n − p + 1) symmetry to prove: ) be an integral, unit-regular and cyclic Brakke flow coming out of C. If there is T > 0 such that M is smooth on (0, T ), then M inherits the O(p + 1) × O(n − p + 1) symmetry (with the same axes of symmetry).There are many other related works on the rotational symmetry of self-expanders. Observe that if there is a unique self-expander asymptotic to a rotationally symmetric cone, then it must inherit the rotational symmetry. The first nontrivial result for double cones is obtained by . They proved that a mean-convex self-expander (i.e. H Σ > 0) asymptotic to a rotationally symmetric double cone is rotationally symmetric. This is later generalized by ) to weakly stable self-expanders. In our previous