From the view of dynamics, analytical expressions of the fatigue crack growth and its rate equations are deduced in series of papers based on static fracture mechanics with thinking about the inertial effect coefficient. According to these analytical expressions, the factors which influence the fatigue crack growth rate are analyzed by the material ability of crack growth and the loading of specimens or structures. The theory can lead to not only quantitatively analysis the above factors, but also reasonably explain some experiment phenomena such as fatigue crack growth rate variations with loading frequency, as the result shows. Some new opinions on the experimental research and engineering applications of fatigue crack growth rate are put forward. For example, K_c and K_(th) are gotten with limited data of fatigue crack growth rate; and the data gotten from laboratory can be used to forecast the engineering structural fatigue life by comparing the inertial effects in the safety condition.