In case of the high performance fibers having high strength and high temperature properties, the wet-laid nonwoven technique is the most suitable method for an isotropic web formation because the dry-laid technique involves many difficulties due to the brittleness of the fiber. Authors have manufactured the nonwovens of high performance fibers on the wet-laid system and investigated the effect of production conditions such as aspect ratio, binder fiber content, and fiber type on the tensile and isotropic characteristic of the nonwovens. The results showed that the breaking stress and initial modulus increased as the aspect ratio increased up to 1200 for carbon nonwovens and to 450 for glass nonwovens, respectively. However, in Oxipan nonwovens, the increase of the aspect ratio gave a slight decrease in the breaking stress with decrease in fiber dispersion in water. The effect of binder content was different depending on the fiber type. In carbon nonwovens, the increase of the binder content resulted in the increase in the breaking stress and initial modulus. In the glass nonwovens, the increase in the breaking stress was found only in the range of the binder content up to 50% and above this range the breaking stress started to decrease.