The invention discloses a lens automatic mounting device and a method. The lens automatic mounting device comprises an ocular lens fitting a feeding mechanism, an ocular lens fitting b feeding mechanism, an ocular lens fitting b oil brushing mechanism, an ocular lens feeding mechanism, an ocular lens mounting mechanism, an ocular lens overturning and screw hitting mechanism, an anti-dazzling screen mounting mechanism, an ocular lens station transmission mechanism, an object lens fitting a feeding mechanism, an object lens fitting b feeding mechanism, an object lens fitting a oil brushing mechanism, a material distributing mechanism, an object lens feeding mechanism, an object lens mounting mechanism, an object lens station transmission mechanism, an object lens and ocular lens mounting mechanism, a double station screw hitting mechanism, and a product material recovering mechanism. The problem of the prior art is that the assembling process of the lens assembly is complicated and low in efficiency. By developing a set of fully-automatic assembling device, the automatic feeding, automatic assembling, automatic material blanking of the lens can be realized, and manual operations can be completely replaced. The precision and yield of lens assembling can be enhanced, and the assembling efficiency of lens can be greatly improved, and the usage demand of practical production can be met.