  The half-size prototype of the multi wire drift chamber (MWDC) for the
cooling storage ring (CSR) external-target experiment (CEE) was assembled and
tested in 350 MeV/u Kr+Fe reactions on the heavy ion research facility in
Lanzhou (HIRFL). The prototype consists of 6 sense layers, where the sense
wires are stretched in three directions X, U and V, meeting $0^\circ$,
$30^\circ$ and $-30^\circ$ with respect to the vertical axis, respectively. The
sensitive area of the prototype is $76 {\rm cm} \times 76 {\rm cm}$. The
amplified and shaped signals from the anode wires are digitized in a serial
capacity array. Being operated with 1500 V high voltage on the anode wires, the
efficiency for each layer is beyond 95\%. The tracking residual is about $301
\pm 2 \rm \mu m$. The performance meets the requirements of CEE.
