The radius power distribution of laser beam is not only a important parameter of beam itself

but also a remakable problem in laser process.The importance of beam mode measuring has interested many research workers working on it since the early 70s.Many methods

including infrared photography

plexiglass burning off

scanning

heat evaporating

thermal deflection of light

interference etc

were developed

but limited of them were applied in China

only plexiglass burning off is in common use.Unfortunately

this method can only offers a statistical result of laser's radiation

but not the real power distribution of the laser beam. In this paper

the needle scanning method is presented which is formed by four units

including scanning

sensing

data acquition and handling.The experiments are also presented.The design capacity of this system permits measuring of beam of 0.2-35mm diameter in 10

2

-10

3

W power level

and the three dimentions power distribution was finally presented by data handling unit.