In order to study the temperature characteristics of the LDMOS 1000W shortwave power amplifier under different temperature, a series of tests have been carried out here. The results showed that Pout, Gain, PAE, two-tone power, second harmonic and third harmonic of the PA decrease dramatically with rising temperature. Meanwhile, when the number of cycles increases from 1 to 5, its Pout, Gain, PAE, two-tone power, second harmonic and third harmonic generally show the downward trend. Further analysis shows that this degradation is caused by the increase of temperature, the decrease of electron mobility and the increase of scattering between electrons and the lattice, which lead to the generation of heat and the intensification of the self-heating effect. At the same time, high temperature also lead to the increase of thermal resistance (Rth), which causes decrease in the efficiency of PA. Therefore, to ensure that the whole amplifier can maintain stable at different temperatures, a temperature compensation circuit is proposed to offset the performance degradation which can provide important reference for the reliability design of PA.