  Using 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, an amplitude analysis of the decay $D_{s}^{+} \to
\pi^{+}\pi^{0}\pi^{0}$ is performed, and the relative fractions and phases of
different intermediate processes are determined. The absolute branching
fraction of the decay $D_{s}^{+} \to \pi^{+}\pi^{0}\pi^{0}$ is measured to be
$(0.50\pm 0.04_{\text{stat}}\pm 0.02_{\text{syst}})\%$. The absolute branching
fraction of the intermediate process $D_{s}^{+} \to f_0(980)\pi^{+},
f_0(980)\to\pi^{0}\pi^{0}$ is determined to be $(0.21\pm 0.03_{\text{stat}}\pm
0.03_{\text{syst}})\%$.
