  By using a two-step method, we successfully synthesized the iron based new
superconductor LaO$_{0.9}$F$_{0.1-x}$FeAs. The Hall effect and
magnetoresistance were measured in wide temperature region. A negative Hall
coefficient R_H has been found implying a dominant conduction by electron-like
charge carriers in this material. The charge carrier density determined at 100K
is about 9.8E20 cm-3, which is close to the cuprate superconductors. It is
further found that the magnetoresistance does not follow the Kohler's law.
Meanwhile, the Hall coefficient, the resistivity at 0T, and magnetoresistance
all have an anomalous property at about 240K, which may be induced by the
multi-band effect or by some exotic scattering mechanism.
