The flow velocity is an important limiting factor behind dynamic light scattering (DLS) measurements for flowing aerosols. In this paper, the autocorrelation function (ACF) of scattering intensity under the laminar flow condition is used to retrieve the simulated and measured DLS data of flowing aerosols, and the restriction of flow velocities on the measurement of the particle size distribution (PSD) for aerosols is analyzed. The results show that the strong influence of velocity increase on the PSD retrieval results cannot be expressed in the ACF model through the contribution of flow velocities. The reason for the difficulty in particle size inversion is that the velocity increase aggravates the ill condition of the ill-conditioned equation where the ACF is located, which is manifested as the increase in the condition number of the kernel matrix in the equation. From the perspective of signal analysis, the increase in flow velocities reduces the amplitude of particle size information in ACF. The influence of flow velocities is related to the particle size of the measured aerosols, and this relevance to particle sizes can be evaluated by comparing the diffusion characteristic time in Brownian motion with the translation characteristic time in aerosol flow. The characteristic time ratio of diffusion to translation can not only characterize the different effects of flow velocities on aerosols with different particle sizes in DLS measurements, but also provide a basis for velocity selection according to the measured objects in actual measurements.