When the self-referencing interferometer wavefront sensor (SRIWFS) is applied to the absolute measurement of wavefront phase, the pinhole diameter should be less than half the Airy-disk diameter (dA) produced by an unaberrated optic so as to obtain a good approximation to a reference plane wave. In this way, however, the intensity transmission is also greatly reduced. To increase the intensity transmission as much as possible and improve the fringe contrast especially in the beginning of closed-loop correction, the maximal pinhole diameter allowed in the closed-loop correction with using SRIWFS is studied. Computer simulation and experiment demonstrate that a pinhole with not greater than 1.5dA can obtain a satisfied correction result and the Strehl ratio after correction is greater than 80%. Additionally, for a plane wavefront the intensity transmission will be increased from 63% to 90% as the pinhole diameter increases from 0.5dA to 1.5dA.