Purpose:This study was designed to investigate difference in isokinetic muscle strength in the knee extensor muscle and characteristic differences in muscle strength between males and females through the ankle joint angles. Methods: Seventy-four subjects participated in this study. There were two groups: 36 males and 38 females. The mean age of the men was 24.58 years and women was 23.74 years. Subjects were seated on a CON-TREX LP (leg press) lean to back of chair, and there bodies were fixed by straps with the hip joint at an angle of $130^{circ}$. After randomly fixing the ankle joint at $0^{circ}$, $20^{circ}$, and $40^{circ}$ of plantar flexion (PF) in range of full extension of knee joint. We studied force max average, force max average/kg, power average, and total work through the angle of the ankle joint when the knee joint was extended from $90^{circ}$ to $180^{circ}$. Results: In the male group, all maximum measured value showed at the ankle joint $0^{circ}$, all minimum measured value showed at $40^{circ}$ PF (p<0.01). In the female group, all maximum measured value showed at the ankle joint $20^{circ}$ PF, especially the power average increased significantly. All minimum measured value showed $40^{circ}$ PF (p<0.01). Conclusion: There are differences between males and females in isokinetic muscle strength of the knee extensor through ankle joint angles in healthy adults. Males and Females have different characteristics of muscle strength through the ankle joint angles.