Question: The power of a lens is the degree by which the lens can bend light, and the absolute refractive index is also the same. What is the difference between them? Is the power of a lens an absolute refractive index of lens?

Answer: 
The index of refraction is a material property. The power of the lens is a characteristic of the lens and depends on the index of the material and the geometry of the lens. From glass with a given index of refraction you can make lenses with different powers, both positive and negative.  

The lens maker's formula shows the relationship between the parameters of the lens:
$$ P=(n-1)( \frac{1}{R\_1}-\frac{1}{R\_2})$$
where n is the index of the glass and $R\_1$,$R\_2$ are the radii of the two surfaces and P is the power of the lens.
The difference is that the refractive index is independent of the shape of the lens, whereas the power is not. Imagine if you had two plain sheets of glass with different values of refractive index- neither would bend light, owing to their shape. Now imagine two lenses made from the same material, one of which is more convex than the other- the more convex lens would end the light more, and thus have more power. If you had two lenses that had the same shape, but one was made of a material with a higher refractive index, that lens would bend light more than the other.