The invention discloses a left and right side mounting device of an engine. The left and right side mounting device of the engine comprises a left and right suspended soft pad assembly of the engine, and a suspended bracket; the left and right suspended soft pad assembly of the engine comprises an elastomer, an upper limiting block and a lower limiting block, wherein both the upper limiting block and the lower limiting block are U-shaped blocks; the elastomer is mounted between bottom plates of the upper limiting block and the lower limiting block; at least one side plate of the lower limiting block; the upper part of an extending part of the lower limiting block is bent toward the inner side to form a limiting part; a buffering part is arranged on the upper limiting block below the limiting part; the suspended bracket comprises a U-shaped vertical connecting block; a horizontal mounting block which is an upwards-opened U-shaped block is connected between extending parts of the lower ends of reinforcing plates at two sides of the vertical connecting block; a positioning pin and a connecting bolt on the bottom plate of the upper limiting block respectively pass through a positioning pin mounting hole and a connecting bolt hole to be fixed on a bottom plate of the horizontal mounting block; engine mounting holes are distributed in the upper part of a vertical plate of a vertical connecting block. With the adoption of the device, the elastomer can be avoided jumping out, and the rigidity is improved.