Organic　materials　are　particularly　appealing　for　circularly　polarized　(CP)　lasers　due　to　their　remarkable　chiroptical　activities　and　exceptional　optical　gain　properties.　However,　conventional　organic　CP　lasers　based　on　chiral　molecules　or　microstructures　typically　exhibit　reciprocal　behavior,　which　complicates　material　synthesis　and　device　fabrication　for　practical　applications.　In　this　study,　we　present　nonreciprocal　CP　lasing　from　achiral　organic　microcrystals　through　the　coupling　between　fluorescence　linear　anisotropy　(f)　and　linear　birefringence　(LB),　known　as　f-LB　effect.　By　carefully　controlling　the　crystallization　process,　we　prepared　triclinic　and　orthorhombic　polymorphs　with　distinct　molecular　packing　arrangements,　which　unlock　the　precise　manipulation　of　f-LB　coupling　for　efficient　polarization　state　conversion　of　photons.　The　triclinic　crystals　exhibited　stronger　f-LB　effect　owing　to　the　suitable　angle　between　the　emission　plane　and　birefringence　axis,　resulting　in　robust　nonreciprocal　CP　luminescence.　More　importantly,　this　coupling　was　further　amplified　during　lasing　oscillation,　ultimately　enabling　nonreciprocal　CP　lasing　with　a　dissymmetry　factor　of　similar　to　1.0.　These　findings　provide　a　novel　approach　to　exploring　high-performance　nonreciprocal　CP　lasers　and　offer　new　insights　into　chiral　photonics　and　optoelectronics.