In a linear Fresnel reflector(LFR), every mirror row was used to track the sunlight in real time and to reflect the sunlight to fixed linear receiver. Therefore, incidence angle and reflected angle of the sunlight and every mirror row tracking tilt angle vary throughout the year. This makes the analysis of shading and blocking between adjacent mirror rows very complex. The calculating formulae of sun shadow length and skew length of LFR mirror row were obtained by the projective method. In order to get the relation of shading and blocking, shadow length and skew length were analysed, for example the minimum mirror row spacing and etc.. Finally, a examples of mirror spacing analysis and relationship of mirror elements arraryment and effective irradiance was given.