<p>Variable-helix cutters perform exceptionally well in chatter suppression and thus have found important applications. However, excellent chatter suppression ability does not necessarily guarantee an ideal machined surface. This paper establishes a variable-helix milling surface topography prediction model based on a novel step-size refining time backtrack (SRTB) method, which considers both the mechanical behavior and geometric characteristics of the variable-helix cutters. The motion trajectories of the cutting elements of each edge with different helix angles are accurately modeled by using a discretization method. The discrete trajectory points calculated roughly are backtracked in a refining time dimension along the cutting trajectory within local regions by SRTB method, thereby achieving precise determination of the peak position of the variable-helix surface texture. A dimension elasticity matrix method is introduced to extract all effective minimum milling envelope trajectory points to constitute the complete 3D surface topography and calculate surface roughness. A series of variable-helix milling experiments well verified the accuracy of the established model. By this model, the effect of variable-helix angle combinations on surface topography and roughness is first investigated. In addition, the influences of cutter runout and cutting vibration are also systematically studied. This research work provides a foundation for the process optimization of the variable-helix milling process.</p>