  The 21 cm signatures induced by moving cosmic string loops are investigated.
Moving cosmic string loops seed filamentary nonlinear objects. We analytically
evaluate the differential 21 cm brightness temperature from these objects. We
show that the brightness temperature reaches 200 mK for a loop whose tension is
about the current upper limit, $G\mu\sim10^{-7}$. We also calculate the angular
power spectrum, assuming scaling in loop distribution. We find that the angular
power spectrum for $G\mu>10^{-8}$ at $z=30$ or $G\mu>10^{-10}$ at $z=20$ can
dominate the spectrum of the primordial density fluctuations. Finally we show
that a future SKA-like observation has the potential to detect the power
spectrum due to loops with $G\mu=10^{-8}$ at $z=20$.
