The invention discloses a measuring method and device for
transmittance of an optical element. The method comprises the steps of splitting a
laser beam with a specific
wavelength to obtain two beams of
laser, enabling the two beams of
laser to pass through a reference light path and a measuring light path respectively, not placing the optical element on the measuring light path, and obtaining energy E1 of the laser beam passing through the reference light path and energy E2 of the laser passing through the measuring light path by measurement; placing the optical element on the measuring light path, and obtaining energy E1' of the laser beam passing through the reference light path and energy E3 of the laser passing through the measuring light path by measurement; and calculating the
transmittance T of the optical element according to an equation T=(E1*E3) / (E1'*E2). According to the measuring method and device, Dual light path aplanatism measurement is adopted, the aim of real-time on-line measurement is achieved, influence of
light source energy shake on
repeatability of measuring results and measurement of the
transmittance of a light-transmission lens can be effectively eliminated, and the transmittance of the optical element used for any
ultraviolet pulse laser can be measured accurately and conveniently.