God has only one throne in heaven, and a Lamb is sitting on His throne.

"And immediately I was in the spirit: and, behold, a throne was set in heaven, and one sat on the throne." - Revelation 4:2

"And I beheld, and, lo, in the midst of the throne and of the four beasts, and in the midst of the elders, stood a Lamb as it had been slain …" - Revelation 5:6

Why is a Lamb on God’s throne?

God took on flesh and blood in the form of the man Jesus Christ to redeem all of humanity from death from their sin by His own death on a cross. (Hebrews 2:14-15)

"Forasmuch then as the children are partakers of flesh and blood, he also himself likewise took part of the same; that through death he might destroy him that had the power of death, that is, the devil; and deliver them who through fear of death were all their lifetime subject to bondage." - Hebrews 2:14-15 KJV

Because God’s flesh was a sacrifice that was holy and without sin, it was called the Lamb of God.

"The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world." - John 1:29

By the blood of JESUS, we have salvation when we repent, are baptized in Jesus name for the remission of sins, and receive the gift of His Holy Ghost. (Acts 2:38, Acts 4:12, Acts 2:4)

Because God’s own flesh and blood was such a great sacrifice of the Creator of the Universe, and by it accomplished the means of salvation for all of humanity, we see God as a Lamb on His throne. His name is JESUS. (Revelation 17:14)