  We develop a pseudo power spectrum technique for measuring the lensing power
spectrum from weak lensing surveys in both the full sky and flat sky limits.
The power spectrum approaches have a number of advantages over the traditional
correlation function approach. We test the pseudo spectrum method by using
numerical simulations with square-shape boundary that include masked regions
with complex configuration due to bright stars and saturated spikes. Even when
25% of total area of the survey is masked, the method recovers the E-mode power
spectrum at a sub-percent precision over a wide range of multipoles
100<l<10000. The systematic error is smaller than the statistical errors
expected for a 2000 square degree survey. The residual B-mode spectrum is well
suppressed in the amplitudes at less than a percent level relative to the
E-mode. We also find that the correlated errors of binned power spectra caused
by the survey geometry effects are not significant. Our method is applicable to
the current and upcoming wide-field lensing surveys.
