Abstract: The laser beam is the most precise and popular instrument to measure the smoke permeate rate. But in most field testing cases, the scene of laser beam light is too small for the smoke field testing and the synchronization problem is also unavoidable when it works at scanning way. In order to insure the measurement precision for the disturbance effect of smoke to the small scene imaging, it introduces the design of lasers array with multi small power same semiconductor laser after beam homogeneous enlarge shaping. The relative variety rate of room permeating rate can be measured by the imaging sensor. It can measure 2.8 m2.8 m smoke at 113.4 m distance with 33 beam homogenous enlarge shaping laser array during the principle test. The scene of CCD is 1010and the error of relative variety rate is less than 0.5% when grey level is no more than 230.