Plasma current control and energy confinement improvement are critical issues in the magnetic fusion research. In this work, the threshold of the fine structure generation and the direction reversal in the drift instability-driven current are identified in tokamak plasmas for the first time based on gyrokinetic simulations. The fine structure current is driven by the ion temperature gradient (ITG) mode, the collisionless trapped electron mode (CTEM), and the electron temperature gradient (ETG) mode. The fundamental properties related to the magnitude and the direction of the fine-scale current are revealed. The fine structure current changes the magnetic topology, modifies the characteristic of turbulence, and reduces the electron heat transport (by 23%) significantly. It is beneficial to the formation of transport barriers near the rational surface. The in-depth knowledge of the turbulence-driven fine structure current provides guidelines in experiments for the control of the current structures and instabilities.