Double-clading fiber coating thermal damage is one of the prime limiting factors for the operation of high-power continuous-wave (CW) fiber lasers. The thermal effects in high power CW fiber lasers are studied, and the maximum output power of fiber lasers limited by the thermal degradation of coatings is theoretically simulated. Theoretical and experimental studies of splice points cooling in 1 kW CW fiber lasers are presented. Thermal contact resistances between the fiber and its heat sink are measured separately for different geometries and efficient cooling methods to achieve effective heat conduction are proposed. By using these optimized methods, based on the master oscillator power amplifier (MOPA) architecture, a 1080 nm 1.11 kW all-fiber laser prototype is obtained. The maximum surface temperature at the pump light launching end splice of the booster amplifier is 327 K (54 ℃). Moreover, thermal or nonlinear effects have not been observed during operation.