Abstract: Fourier heat transfer model and solid-liquid couple method were used to analyze the thermal characteristics of thin-wall metal under nanosecond laser pulse. The high-power heat source operated with a fixed pulse width of 30 ns. It is found that the changes of fluid and solid wall temperature depend on operating time. During an individual pulse, the inside temperature in solid wall increases rapidly within 30 ns pulse heating period, then begins to decrease after 1ms. After 50 ms, the radial distribution of solid temperature becomes uniform gradually. Under the repetitively operated pulse with 40 Hz frequency, the wall temperature oscillates with the same frequency. After a certain time, the temperature oscillation becomes equilibrium and changes within a certain range. If the pulse heating is stopped, both the fluid and wall temperature will sharply decrease to the initial values within 2 s. The effects of fluid flow rate and physical properties of solid wall are also discussed. Both the increase of flow rate and solid thermal diffusivity can decrease the wall temperature and accelerate thermal balance.