Space　truss　structures　are　essential　components　for　space-based　remote　sensing　loads　with　high　spatial　and　temporal　resolutions.　To　achieve　high-precision　vibration　control,　an　accurate　and　efficient　dynamics　model　is　essential.　In　addition　to　the　current　equivalent　beam　model　(EBM)　based　on　the　classical　continuum　theory,　an　improved　equivalent　beam　model　(IEBM)　is　proposed　that　considers　the　impact　of　the　distinction　between　trusses　and　beams　on　torsional　and　shear　deformations,　as　well　as　the　impact　of　shear　deformation　on　flexural　rigidity.　According　to　the　displacement　expressions　of　spatial　beams,　torsional,　shear,　and　bending　correction　coefficients　are　introduced　to　derive　expressions　of　strain　energy　and　kinetic　energy.　The　energy　equivalence　principle　is　then　utilized　to　calculate　the　elasticity　and　inertia　matrices,　and　dynamics　equations　are　established　using　the　finite　element　method.　Subsequently,　an　IEBM　is　constructed　by　employing　the　particle　swarm　optimization　approach　to　determine　the　correction　coefficients　with　the　truss　natural　frequency　as　the　optimization　target.　The　natural　vibration　characteristics　of　the　structure　are　estimated　for　various　material　properties.　Compared　with　the　full-scale　finite　element　model,　the　EBM　reaches　a　maximum　error　of　80%　for　a　low　modulus　of　elasticity,　while　the　maximum　error　of　the　IEBM　is　less　than　2%　for　any　given　parameters,　indicating　its　superior　accuracy　to　the　EBM.　©　2023