The improved photoenhancement of the SAW convolution effect in monolithic convolvers with high-resistivity surface layer has been discussed. CdS monolithic convolvers with one or a half acoustical wavelength thick high-resistivity layer formed on semiconductive substrate are prepared in order to check the expected behavior. Due to much reduction of the acoustoelectric loss of SAW, the convolver with a half acoustical wavelength thick high-resistivity layer shows a remarkable photoenhancement, 20 times the value in the dark, when photocarriers are generated uniformly in the high-resistivity layer. Nonlinear capacitance mechanism can also induce photoenhancement of the convolution effect. It is first found that further enhancement of the convolution can be achieved by applying positive pulsed bias to the gate electrode under illumination of a light with high absorption coefficient.