Abstract: The wave radiation stress is the main driving force of wave induced longshore current and even nearshore current. It is directly related to the size and hydrodynamic characteristics of longshore current whether the calculation of the wave radiation stress is accurate or not. Irregular waves are more capable of reacting wave motion in the ocean compared to regular waves. Therefore, the calculation of the radiation stress under irregular waves will be more able to reflect the wave driving force in the actual longshore current. The exact solution and approximate solution of the irregular wave radiation stress are derived and compared with the two kinds of calculation methods. On the basis of this, the experimental results of wave-driven longshore currents are used to verify the calculation of wave energy in the approximate calculation method. The results show that: the approximate calculation method of irregular wave radiation stress has a good accuracy under the condition of narrow spectrum, which can save a lot of computing time and thus improve the efficiency of calculation. However, the exact calculation method can accurately reflect the fluctuation of radiation stress at each moment and each location.