This invention provides an image capturing lens assembly in order from an object side to an image side comprising: a first lens group has only one first lens element with a positive refractive power, and a second lens group in order from the object side to the image side comprising: a second lens element with a negative refractive power, a third lens element, a fourth lens element and a fifth lens element; while a distance between an imaged object and the image capturing lens assembly changes from far to near, focusing is performed by moving the first lens group along the optical axis and a distance between the first lens group and an image plane changes from near to far. By such arrangement and focusing adjustment method, good image quality is achieved and less power is consumed.