Poly　(triazine　imide)　photocatalysts　prepared　via　molten　salt　methods　emerge　as　promising　polymer　semiconductors　with　one-step　excitation　capacity　of　overall　water　splitting.　Unveiling　the　molecular　conjugation,　nucleation,　and　crystallization　processes　of　PTI　crystals　is　crucial　for　their　controllable　structure　design.　Herein,　microscopy　characterization　was　conducted　at　the　PTI　crystallization　front　from　meso　to　nano　scales.　The　heptazine-based　precursor　was　found　to　depolymerize　to　triazine　monomers　within　molten　salts　and　KCl　cubes　precipitate　as　the　leading　cores　that　guide　the　directional　stacking　of　PTI　molecular　units　to　form　aggregated　crystals.　Upon　this　discovery,　PTI　crystals　with　improved　dispersibility　and　enhanced　photocatalytic　performance　were　obtained　by　tailoring　the　crystallization　fronts.　This　study　advances　insights　into　the　directional　assembling　of　PTI　monomers　on　salt　templates,　placing　a　theoretical　foundation　for　the　ordered　condensation　of　polymer　crystals.