Conformal-coating technology of power white LEDs uses PVA+ADC water-solution compounding yellow phosphor to coat on the surface of the die,then gets planar structure of the phosphor though exposure and developing. The luminous efficacy of the white LEDs is finally increased (higher than 100 lm/W for one die) though optimizing the technology including the stabilization of processing step and exposure time,confining the every element including comparison experiment of darkroom and the control of temperature. It is stabilized in color temperature of 5000 K and luminous efficacy of 90 lm/W.