[en] Fatigue crack growth tests were carried out using CT specimen under the conditions of stress ratio R=0.1, 0.3, 0.5 for imported maraging steel(VAR), domestic maraging steel(ESR) and AISI4337-V steel. The near-threshold values, stable crack growth chracteristics and the behavior of crack closure were investigated. In the region of near-threshold fatigue crack growth, ΔKth decrease sharply from stress ratio R=0.1 to R=0.3 gradually over stress ratio R=0.3. Constant m increase and constants C decrease under increasing stress ratio respectively. And the gradient of fatigue crack growth rate decrease in the order of AISI 4337-V steel, ERS and VAR in the region of stable fatigue crack growth. If fatigue crack growth rate are evaluated by using ΔKeff which are calculated at the crack closure point, da/dN fits with one stright line independently of stress ratio. And the effective stress intensity factor range ratio U is the function of only Kmax.(Author)