The slope and curvature hybrid wavefront sensing technique can realize the precision measurement of high-order aberration by using all the first and second derivative information of the wavefront in the subaperture. And it is an important development direction of zonal wavefront sensing technology. Based on the slope and curvature hybrid wavefront sensor used subaperture amplitude modulation, a slope and curvature signal extraction algorithm was proposed. The centroid detection algorithm was utilized to realize the direct measurement of wavefront slope, Laplacian curvature and twist curvature in each subaperture. The simulation results show that the detection accuracy of the slope and curvature signals are all within 0.02λ(λ=632.8 nm) under the ideal condition. In the case where the noise level is less than 10%, the detection accuracy of the slope and curvature signals are all within 0.08λ. The algorithm has high detection precision and good noise immunity.