A model to simulate SMPS (Scanning Mobility Particle Sizer) measurement and the associated uncertainty analysis when axial DMA (Di erential Mobility Analyser) classi er operates under scanning mode conditions is de- scribed. Starting from simulated SMPS raw data, a fast estimation of aerosol size distribution measurement using regularization technique is performed. Then, global sensi- tivity analysis is used to discriminate signi cant parameters of the system and, as a preliminary result, a 95% con dence region is obtained by Monte Carlo simulations on an atmo- spheric aerosol size distribution.