The invention relates to a method for determining at least one beam propagation parameter (M2, w0, θ, z0) of a laser beam, comprising: directing the laser beam through a lens arrangement towards a spatially resolving detector, imaging the laser beam at a plurality of different focus positions (F1, . . . ) relative to the spatially resolving detector by adjusting a focal length (f1, . . . ) of the lens arrangement, and determining the at least one beam propagation parameter (M2, w0, θ, z0) by evaluating an intensity distribution (l(x,y)) of the laser beam on the spatially resolving detector at the plurality of different focus positions (F1, . . . ). The method comprises adjusting the focal length (f1, . . . ) of the lens arrangement by arranging lens elements (A1, . . . ; B1, . . . ) having different focal lengths (fA1, . . . ; fB1, . . . ) in a beam path of the laser beam.