The branch points in laser propagation through atmosphere are detected with 30×30 HartmannShack wave-front sensor. It is shown that there is branch points in beacon light phase in strong scintillation, and the results agree with the simulated data. It is proved that branch points appear in pair. The branch point problem is computed by four-dimension code of laser propagating in atmosphere. The effects of emission diameter and grid precision on the position and account of branch points are analyzed.