The invention aims to provide a testing device for a plastic housing of an air conditioner. The testing device comprises two mounting bases which are arranged front and back, wherein mounting blocks are arranged at the tops of the mounting bases for mounting the plastic housing of the air conditioner; rotary motors are arranged at the left side and the right side of the two mounting bases; a rotating shaft is connected to the top of each rotary motor; a rotary bar is connected to the top of each rotating shaft; a mounting head is connected to the top end of the inner side of each rotary bar; an impact test head is connected to the inner side of each mounting head; and the impact test heads can rotate toward the inner sides to be located between the two mounting bases, so that the impact test heads are in contact with the plastic housing of the air conditioner, mounted on the mounting blocks, for impact testing. A part to be tested is mounted between the two mounting blocks, and after that, the rotary motors are started to drive the rotary bars to rotate toward the inner sides, so that the impact test heads are in contact with the plastic housing of the air conditioner, mounted on the mounting blocks, for impact testing; the rotary motors at the left side and the right side perform an impact test in turns, so that test can be made efficiently and quickly; and the testing deviceis good in effect, high in efficiency and suitable for a production test.