The invention discloses rigid polyester engineering plastic with a high smelting point and a high glass-transition temperature. The plastic is prepared by synthesizing the following raw materials in parts by weight: 1,000 to 1,200 parts of dioctyl phthalate monomer, 400 to 700 parts of dihydric alcohol monomer, 100 to 350 parts of phenolphthalein, 0.5 to 2 parts of catalyst, 1 to 4 parts of stabilizer and 1 to 8 parts of antioxidant. The plastic has the advantages of excellent heat resistance, excellent aging resistance, simple preparation method, longer service life, high toughness, high fatigue resistance, excellent environment resistance, outstanding flame retardance and outstanding low smokiness, and is an ideal high molecular material for use in the high-tech fields of electronic and electric industry, mechanical industry and the like.