The main figure of the State Emblem of Georgia is Saint George, that is symbolically expressed as a red right-angled cross against a white background (in heraldry - a "purple" (red) right-angled cross on a silver field) in armory and vexillology (as well as in sacral and secular symbolism). 
Saint George, as a symbol of united Georgia, i.e. an embodiment and patron of Georgia, was first depicted on a big state seal of King George III (1115-1184). An unknown chronicler of King David IV the Builder writes that in 1121, in The Battle of Didgori, "Saint George the Martyr was leading Georgian army obviously and visibly." In 
his work Notifications of Foreign Pilgrims on Georgian Monks and Georgian Monasteries, Grigol Peradze, who studied historic sources about the origin of the name GEORGIA, gives a quite interesting notification, dated presumably by 1180, from a work of Latin Patriarch of
Jerusalem, Jacques de Vitry (approx. 1160/70-1240), The History of Jerusalem - "these people are called Georgians, as they treat with particular reverence and adore Saint George, who they consider as their patron and standard-bearer... and respect him more than any other Saints." And Johann Count of Solms writs in 1483: "there is one more nation living far from Jerusalem... they are called Georgians, according to the name of Saint George, who they have chosen as their patron." This is interesting that, according to one of Georgian legends, which is given by Ioane Batonishvili (prince) in his novel Kalmasoba, David IV the Builder "saw a horse having horns at a narrow place of Mtskheta. The King called him and the horse came to theking, and the king caught him, and slaves of the king came and the king ordered to saddle the horse and put a bridle on the horse of Saint George." 
According to Teimuraz Batonishvili (prince), "Georgian kings depicted face of Saint George the Martyr on their State Emblems, and his face was considered to come first for the State of Georgians."
Silver Saint George on a "purple" (red) field as a State Emblem is given by Valkhushti
Batonishvili (prince) on his 1735 map of Georgia and Caucasus. This is presented on a 1784 Big State Seale of King Erekle II as well. Saint George, as a main figure of the State Emblem of Georgia is mentioned in foreign sources as well: in 1672 so
called Titularnik by Russian king Aleksey Mikhailovich; in 1698 travel report of Johann Georg 
Korb, ambassador of Austrian Imperator Leopold I, etc.
In the State Emblem of Georgia, Royal Crown of Georgia is used as a mark of state sovereignty, which is known as Iveria Crown in international heraldry.
As for golden lions holding a shield, this is given according to images of State Emblems of kings of Georgia Levan, Kaikhosro, Georg XI, Vakhtang VI, Erekle II, George XII and David XII the Governor.
Author of the Georgian State Emblem: painter Mamuka Gongadze
State council of heraldry
at the Parliament of Georgia