The extinction-to-backscatter ratio (also called lidar ratio-LR) is an important parameter which provides information on the transmission and reflection properties of cirrus clouds and also on the ice crystal properties due to their dependence on the particle shape, size and orientation for the particles. In this study is showed an innovative method to obtain theLR for each cloud layer through iterative processes, applying a numerical routine developed at the Center for Lasers and Applications (CLA/IPEN-Brazil) in cooperation with the Laboratoire Amosphères, Milieus, Observations Spatiales, Institut Pierre Simon Laplace/Versailles-Saint Quentin University (LATMOS/IPSL-France). The resulting LR values were obtained based on measurements of the MSP (Metropolitan City of São Paulo) - lidar system, performed on 11th June 2007, comprehending 298 minutes separated in 7 distinct so called stationary periods. For the first four periods, was observed two distinct layers of clouds with LR values varying between 28±15 and 35 ± 18 sr for the first layer and 37±11srand 74±14 sr for the second, indicating the presence of both small and large ice crystals composed by solid and hollow columns in majority. The last 3 periods of measurements in turn presented a mono¬layer cloud with LR about 19±04 sr, what corresponds to a relatively small solid needles, plates and column crystals.