The Chang 6 fractured low-permeability reservoir of the Wuqi W block is characterized by highly developed microfractures，limited waterflood sweep efficiency，and the formation of dominant flow channels during long-term water injection，which make conventional plugging agents ineffective for deep profile control. Based on the above issues，a pre-assembled core-shell phase-change profile control agent （TSAD） was developed using a multi-component modified epoxy resin system as the core and a biopolysaccharide as the outer shell，enabling deep migration and temperature-induced phase-transition solidification to meet the requirements of deep profile control in fractured low-permeability reservoirs. Dynamic light scattering，rotational viscometry，microfracture piston extrusion，and core flooding experiments were employed to systematically investigate the particle size distribution，phase-transition characteristics，plugging strength，water-plugging and oil-displacement performance of TSAD. The results showed that TSAD exhibited a particle size distribution of 20 — 300 nm after phase transition，indicating excellent injectivity；the phase-transition time could be adjusted within 5 — 12 days，which could meet the requirements of deep profile control. The plugging strength increased with the increase of injection mass fraction. TSAD achieved a breakthrough pressure of 8 . 56 MPa and a stable pressure of 8 . 02 MPa at 2 . 5 % mass fraction，meeting the strength requirements for deep plugging. The phase-transition behavior was not affected by the pH or salinity of field formation water. Core flooding tests demonstrated a plugging rate of 80 . 69 % in high-permeability cores and only 3 . 1 % in low-permeability cores under injection of 0 . 3 PV 1 . 0 % TSAD，with the oil displacement efficiency in low-permeability core improved by 13 . 44 percentage points，confirming its capability to effectively block dominant channels of fractures and enhance oil recovery. A field pilot test was conducted in the X-XX well group of the Chang 6 reservoir in the Wuqi W block. The water cut decreased by 25 . 85 %，and the daily oil production increased from 5 . 84 t to 7 . 33 t，achieving an incremental oil production of 1 . 49 t/d. These results demonstrate that TSAD provides excellent deep-profile control performance in fractured low-permeability reservoirs，offering a new and effective technical approach for water control and enhanced oil recovery.