Laser anemometry system comprising: - an assembly of at least one coherent laser source which provides an incident beam, the beam being retrodiffused by a group of particles which pass through the incident beam, - mixing means, which are respectively associated with a laser source, for the retrodiffused beam and a reference beam, the reference beam being the duplication of the incident beam, creating a wave of interferometry, - conversion means, which are respectively associated with a laser source, which convert the wave into an electrical signal whose instantaneous intensity is proportional to the instantaneous power of the wave, - first means, which are respectively associated with a laser source, for determining a time/frequency graph of the electrical signal, - second means, which are respectively associated with a laser source, for determining tasks of the graph, each task being a group of connected points of the graph, having exceeded a detection threshold, - calculation means, which are respectively associated with a laser source, for calculating a mean of the frequency, a duration and a gradient which characterise the development of the frequency in accordance with time in the time/frequency graph associated with a task, respectively, characterised in that it further comprises: - third means for determining the air speed from all or some of the means of the frequency, the durations and the gradients, the third determination means further being capable of calculating a Doppler frequency, the Doppler frequency being the mean of all or some of the means of the frequency which are associated with tasks for which the following condition is verified, respectively: the multiplication of the gradient by the square of the duration is less than a predetermined threshold. - an assembly of at least one coherent laser source which provides an incident beam, the beam being retrodiffused by a group of particles which pass through the incident beam, - mixing means, which are respectively associated with a laser source, for the retrodiffused beam and a reference beam, the reference beam being the duplication of the incident beam, creating a wave of interferometry, - conversion means, which are respectively associated with a laser source, which convert the wave into an electrical signal whose instantaneous intensity is proportional to the instantaneous power of the wave, - first means, which are respectively associated with a laser source, for determining a time/frequency graph of the electrical signal, - second means, which are respectively associated with a laser source, for determining tasks of the graph, each task being a group of connected points of the graph, having exceeded a detection threshold, - calculation means, which are respectively associated with a laser source, for calculating a mean of the frequency, a duration and a gradient which characterise the development of the frequency in accordance with time in the time/frequency graph associated with a task, respectively, - third means for determining the air speed from all or some of the means of the frequency, the durations and the gradients, the third determination means further being capable of calculating a Doppler frequency, the Doppler frequency being the mean of all or some of the means of the frequency which are associated with tasks for which the following condition is verified, respectively: the multiplication of the gradient by the square of the duration is less than a predetermined threshold.