The invention provides a special fixture and method for mounting a core pipe of an OVD sintering quartz furnace. The fixture comprises a connection top plate and a hoisting component and an adjusting component arranged on the connection top plate, wherein the hoisting component comprises a left ring device, a middle ring device and a right ring device arranged on the connection top plate in an equal interval; the adjusting component comprises multiple adjusting devices uniformly arranged along the outer circumference of the connection top plate; the adjusting device comprises a radial adjusting plate mounted on the connection top plate through a first connector and an axial adjusting plate mounted on the radial adjusting plate through a second connector; a connection top plate buffer pad is arranged on the lower side of the connection top plate; and an axial adjusting plate buffer pad is arranged on the axial adjusting plate. The fixture provided by the invention has an adjustment function along the axial and radial directions of the core pipe of the quartz furnace; and since a buffer pad is fixed on the part in contact with the core pipe of the quartz furnace, direct contact between metal and the core pipe of the quartz furnace is avoided, and the core pipe of the quartz furnace is prevented from cracking under impact force in a hoisting process.