  A new method is proposed to reconstruct the neutrinos in the $e^+e^-\to Zh$
process followed by the $h\to\tau\tau$ decay. With the help of a refined Higgs
momentum reconstruction from the recoiling system and the impact parameters,
high precision in the determination of the momentum of neutrinos can be
achieved. The prospect of measuring the Higgs CP mixing angle with the
$h\to\tau\tau$ decay at future $e^+e^-$ colliders is studied with the new
method. The analysis is based on a detailed detector simulation of the signal
and backgrounds. The fully reconstructed neutrinos and also other visible
products from the tau decay are used to build matrix element (ME) based CP
observables. With 5 $ab^{-1}$ of data at $E_{\text{CM}}=250$ GeV, a precision
of $2.9^\circ$ can be achieved for the CP mixing angle with three main
one-prong decay modes of the taus. The precision is found to be about 35\%
better than the other methods.
