As a critical component of high-performance aerospace engines, the blisk poses significant challenges to manufacturing technology due to its complex structure and poor machinability. To address the wide-path machining demand of blisk blade surfaces, this paper proposes an improved variable chordal trajectory planning method. First, the blade surface was reconstructed. Taking the concave-convex properties of the blade surface and tool machine tool motion constraints as the criteria, the design principles for drum grinding wheels were extended. Then, the reconstructed surface was trimmed according to the actual machining area, and the grinding trajectory of the wheel was planned by considering the influence of blade surface curvature variation in the tool path direction on chord height error. The results show that compared with the drum grinding wheel designed by traditional methods, the one designed based on the extended principles reduces the number of tool paths from 41 to 32 under the same conditions, effectively increasing the machining row width. The improved planning method can also control the chord height error within the allowable range. Simulations with different grinding wheels show that the standard deviation of undercut is reduced from 9.42 μm to 5.27 μm, and from 2.82 μm to 1.98 μm, respectively, resulting in a more uniform undercut distribution.