According to the practical needs of the shipborne infrared warning systems, the infrared radiation features of low altitude anti-ship missiles under the background of sea and sky are studied and an erected predigest infrared radiation model is established. The infrared radiation intensity of some type anti-ship missile in the long waveband (the main operation waveband of infrared warning system) is calculated from three main radiation sources including pout, flame and skin of the missile. An analysis of the calculation result is made finally.