  We measure the resistance oscillation of quantum point contact (QPC) under
microwave (MW) radiation. What is different from the common resistance
oscillation induced by edge magnetoplasmon (EMP) is that at lower magnetic
field ({\omega}>{\omega}_c), photoconductance is positive (negative) with weak
(strong) MW radiation. This transport phenomenon is proved to be related to
superballistic flow of electrons through QPC. The distinction between the
regions {\omega}>{\omega}_c and {\omega}<{\omega}_c is attributed to different
absorption rate of MW radiation. Violent absorption occurs when cyclotron
orbits or current domains are destroyed in QPC region.
