It　is　necessary　for　calculating　the　solar　beam　radiation　on　the　tilted　mirror　or　aperture　for　designing　of　solar　thermal　utilization.　Linear　Fresnel　reflector　(LFR)　can　be　thought　that　smooth　linear　optical　reflector　is　broken　into　segments.　Every　mirror　segment　or　row　of　this　kind　concentrator　needs　to　track　the　sun　real　time　and　reflects　the　sunlight　to　fixed　linear　receiver.　Therefore,　the　incidence　angle　and　the　direction　of　reflected　sunlight　and　tracking　tilt-angle　of　every　mirror　row　consequentially　vary　throughout　the　year,　which　makes　the　optical　analysis,　especially　the　calculation　of　the　solar　beam　radiation　received　by　full　mirror　field　,　very　complexity.　This　paper　firstly　derived　the　equations　of　incidence　angle　and　tracking　inclination　angle　by　vector　analysis,　and　then　computed　the　instantaneous　solar　beam　radiation　of　all　mirror　elements.　Finally,　cumulated　irradiation　of　whole　mirror　field　during　the　available　work　was　obtained.　The　algorithm　of　optimal　tower　highness　of　LFR　mirror　field　was　derived　by　analyzing　excursion　of　reflecting　sunlight.　©　All　Rights　Reserved.