Abstract: In order to measure laser power accurately under oblique incidence, a correction method for power responsivity of array detectors according to incidence angle is adopted. The expressions of directional cosines and incidence angle depending on the position of laser source, and the position and attitude angle of array detectors are derived. Measurement uncertainties of directional cosines, incidence angle and correction factor of array detectors are derived. The measurement uncertainty expression of laser power is then derived based on the expression of laser power. Therefore the measurement method of laser power and the evaluation method of the power measurement uncertainty under oblique incidence are completely developed. For an example with typical parameters, the power measurement uncertainty under oblique incidence is calculated. The result shows that it is valid to correct the measured laser power for the decrement of measurement uncertainty. Key words: