Abstract: The new designed fiber end-pump coupling device was reported to solve the problem in a monolithic fiber system outputting higher level of signal power, which was limited by pump brightness and temperature control of the pump injection area. By enlarging the signal fiber cladding diameter, more pump power could be injected in fiber system and the temperature of the pump injection area was successfully reduced. In experiment, 9.95 kW pump laser was injected to a monolithic fiber laser system, and over 6 kW signal output was realized. This fiber end-pump coupling device is capable of 10 kW class pump injection and promising for the application in a 10 kW class monolithic fiber laser system.