Abstract: Trying to define the character of Greek art, Winckelmann chose the Laocoon Group as an expression of “noble simplicity and calm grandeur” (“die edleEinfalt, die stilleGrösse”) in 1755 when he was in Dresden. This article proves that the Laocoon Group Winckelmann described is neither the original Roman copy in Vatican Belvedere, nor a plaster copy, but a bronze copy by a French sculptor in the 17th century. However, Winckelmann found the quality of simplicity and grandeur in Laocoon’s facial expression and gesture. After Winckelmann traveled to Roman and observed the authentic Roman copy, he invented a different theory about Laocoon’s expression and gesture. This article also argues that the sculpture’s gesture, especially the right arm of Laocoon Winckelmann saw in Dresden and Rome was actually adapted by Renaissance artists. Consequently, Winckelmann’s 1755 theory of Laocoon should be reconsidered under the perspective of archelogy and the history of copying and restoration of antiques.