  Motivated by the novel phenomena observed in the layered material $\rm
SrCu_2(BO_3)_2$, the Shastry-Sutherland model (SSM) has been extensively
studied as the minimal model for $\rm SrCu_2(BO_3)_2$. However, the nature of
its quantum phase transition from the plaquette valence-bond solid (PVBS) to
antiferromagnetic (AFM) phase is under fierce debate, posing a challenge to
understand the underlying quantum criticality. Via the state-of-the-art tensor
network simulations, we study the ground state of the SSM on large-scale size
up to $20 \times 20$ sites. We identify the continuous transition nature
accompanied by an emergent O(4) symmetry between the PVBS and AFM phase, which
strongly suggests a deconfined quantum critical point (DQCP). Furthermore, we
map out the phase diagram of an extended SSM that can be continuously tuned to
the SSM, which demonstrates the same DQCP phenomena along a whole critical
line. Our results indicate a compelling scenario for understanding the origin
of the proposed proximate DQCP in recent experiments of $\rm SrCu_2(BO_3)_2$.
