This paper reports some measurement results of the characters of the transmitting laser light produced in laser heating micro-balloon targets. The transmitting images of the micro-balloon targets are transparent in the case of accurate focusing and small prepulse. But its images are muddy in the case of defocusing and larger prepulse. The measurement results obtained by using the spatial resolve spectrum show that the spectrum of the transmitting laser light passed through the plasma is broadened clearly, the broadened spectrum line is central symmetry to the spectral line of the input laser beam, the width of the spectrum is broadened from 0.2 nm to 5.0 nm.