  Utilizing a data set corresponding to an integrated luminosity of 6.32~$\rm
fb^{-1}$, recorded by the BESIII detector at center-of-mass energies between
4.178 and 4.226~GeV, we perform an amplitude analysis of the decay $D_{s}^{+}
\to K_{S}^{0}\pi^{+}\pi^{0}$ and determine the relative fractions and phase
differences of different intermediate processes, which include
$K_{S}^{0}\rho(770)^{+}$, $K_{S}^{0}\rho(1450)^{+}$, $K^{*}(892)^{0}\pi^{+}$,
$K^{*}(892)^{+}\pi^{0}$, and $K^{*}(1410)^{0}\pi^{+}$. Using a double-tag
technique, and making an efficiency correction that relies on our knowledge of
the phase-space distribution of the decays coming from the amplitude analysis,
  the absolute branching fraction is measured to be $\mathcal{B}(D_{s}^{+} \to
K_{S}^{0}\pi^{+}\pi^{0})=(5.43\pm0.30_{\text{stat}}\pm
0.15_{\text{syst}})\times 10^{-3}$.
