A light guide plate includes a light input surface and a light output surface adjoining the light input surface. The light output surface defines a first portion adjacent to the light input surface, a second portion connected with the first portion away from the light input surface. The light guide plate further includes a plurality of prism lenses arranged on the second portion, each prism lens extending along a direction perpendicular to the light input surface, and a plurality of tetrahedral lenses arranged on the first portion of the light output surface, each tetrahedral lens having a side surface located at an imaginary boundary line perpendicularly to the light output surface. A relative height of each tetrahedral lens progressively increases with increasing distance from the light input surface. The present light guide plate and a backlight module using the same can efficiently decrease interference.