Abstract Beam diffraction management with on‐demand efficiency over compact devices is important in various applications, such as communications, spectroscopy, wireless power transfer, and others. Recently, the in‐depth study of metasurfaces, such as phase gradient metasurfaces (PGMs) or metagratings (MGs) made of discrete elements, has promoted an ultrathin platform to manipulate diffractions. However, most studies only focus on symmetrical diffraction orders or different propagating diffraction orders with equally distributed energy. It is difficult to efficiently excite beams with arbitrary energy distribution by phase‐only metasurfaces due to the complex optimization procedure. Here, to address these challenges, Fourier harmonic component engineering is proposed to allocate the energy between multiple diffraction beams. By introducing phase‐corrected gradient (PCG) on the metasurface platform, lossless transformation from the incidence to far‐field patterns can be obtained. A variety of diffraction situations are considered (symmetric and asymmetric, with equal or arbitrary energy ratio), where the simulated and measured far‐field patterns are in excellent agreement with the theoretical predictions and the achieved diffraction efficiency is up to 98.3%. The proposed method paves the way for multichannel wireless communication applications and can be readily extended to other frequency regions.