A method for manufacturing an LED module includes following steps: providing a SMT apparatus having a CCD image sensor, providing a PCB having an LED mounted on, and fixing the PCB in the SMT apparatus; providing a lens, the CCD image sensor imaging the lens, and then the SMT apparatus obtaining a location of the lens relative to the LED, and the SMT apparatus positioning the lens on the PCB to cover the LED; providing an optical diffusing board located above the lens, and electrifying the LED for emitting light towards the optical diffusing board; providing a luminance colorimeter to measure luminance and chroma of light exited from the optical diffusing board, and obtaining a light-emitting data; calculating the light-emitting data, and the SMT apparatus adjusting a position of the lens relative to the LED; and fixing the lens on the PCB.