The appcarance of a temporal irrcgularity of acrodynamic force of a rectangular cylinder with the critical depth (D/H=0.6), seems to be such startling phenomenon that is well worth investigating further. In this paper, turbulent flow around a stationary rectangular cylinder with the side ratio D/H of 0.2 to 1.0, has been computed by the LES method at high Reynolds number of 2.2×104. The Smagorinsky model was used as a subgrid scale (SGS) model. The main objcctives of this work are to predict and evaluate characteristics of flows for a stationary cylinder. The computational results of force coefficients such as mean and fluctuating values of drag and lift forces, Strouhal number and flow-configurations correspond well with experimental data. We confirm that the abrupt changes of the aerodynamics forces appear irregularly with the time for the cylinder with a critical section. The temporal variation of a drag force between low and high values is certified to be accompanied with the corresponding change of instantenious frequency of lift force, by using of a wavelet transform method and an analysis of frequency histogram. The time history of drag force CD agrees well with variation of the intensity of the wavelet transform coefficients or Strauhal number from the wavelet analysis results of lift force CL.