This work studies the friction and wear behaviors of chromium (hard material) and crystalline cellulose (soft material) under water lubrication considering the loading and sliding velocity on friction force, temperature of contact interfaces, and worn atoms from the atomic view. The change of friction force with sliding velocity is greater than that with loading, and it is easier to obtain a stable friction at high velocity. The average friction force in the stabilization gradually increases with loading and velocity, and the growth rate decreases with loading, while it increases with velocity. The temperature of contact interfaces at the beginning of sliding changes rapidly and gradually becomes stable. The temperature at the stabilization increases distinctly with velocity, while it does not change much with loading. Both the loading and sliding velocity have an important influence on the wear of soft material; it is noticed that the amount of worn atoms increases close to exponentially with velocity and linearly with loading. However, the wear of hard material changes less with increasing loading and sliding velocity.