The　development　of　laser　heterodyne　interferometry　raises　the　requirements　of　measurement　resolution　and　accuracy.　However,　periodic　nonlinearity　errors　mainly　suppress　the　accuracy　of　laser　heterodyne　interferometry.　Based　on　the　generation　mechanism　of　nonlinearity　errors,　the　sources　of　nonlinearity　errors　in　laser　heterodyne　interferometry　are　first　analyzed　in　this　paper.　Then,　a　synthetic　model　is　established　to　analyze　the　influences　of　various　nonlinearity　error　sources　on　the　first-　and　second-harmonic　nonlinearity　errors.　The　first-　harmonic　nonlinearity　errors　can　be　reduced　and　suppressed　by　adjusting　the　orientation　error　of　optical　elements　in　a　heterodyne　interferometer.　Furthermore,　the　azimuthal　misalignment　of　the　polarization　beam　splitter　(PBS)　is　the　main　source　of　the　second-harmonic　nonlinearity　errors.　Therefore,　when　in　heterodyne　interferometer,　the　azimuthal　misalignment　of　the　PBS　should　be　avoided　if　possible.　This　study　provides　theoretical　basis　for　reducing　and　compensating　nonlinearity　errors　in　a　laser　heterodyne　interferometer.　(C)　2018　Optical　Society　of　America