  We report a continuous phase transition between quantum-anomalous-Hall and
trivial-insulator phases in a magnetic topological insulator upon magnetization
rotation. The Hall conductivity transits from one plateau of quantized Hall
conductivity $e^2/h$ to the other plateau of zero Hall conductivity. The
transition curves taken at various temperatures cross almost at a single point,
exemplifying the critical behavior of the transition. The slope of the
transition curves follows a power-law temperature dependence with a critical
exponent of $-0.61$. This suggests a common underlying origin in the plateau
transitions between the QAH and quantum Hall systems, which is a percolation of
one-dimensional chiral edge channels.
