A high precision laser screen dispersion measurement method based on the line laser parallel detector array composite was presented to solve the difficulty of barrage weapons location dispersion test. The principle of measuring shell coordinate based on line laser parallel detector array composite was researched. Impact points coordinate algorithm was derived and the impact points coordinate algorithm flow chart was presented. Algorithm errors caused by laser detector array precision was analyzed, coordinate errors distribution of coordinates positions and target area were researched. The analysis results indicate that maximum theoretical x negative innate errors increases by 3.44 mm, from 1.56 mm to 5 mm and the maximum y innate errors was 2 mm when the regular target area increased from 3 m×3 m to 10 m×10 m unless small area with high errors. Tests have done with the proto whose target area was 1 m×1 m, the results show that the maximum x errors was 3.6 mm, and the maximum y errors was 2.8 mm when the precision of detector array was 1.6 mm. This measuring method has the advantages of high measuring precision, easy to construct large target area, easy to install.