Abstract: The grid-connected proportion of distributed generation (DG) in the distribution network will continue to increase in the future. Therefore, this paper proposes the definition and calculation method of DG penetration limit values of distribution network. First, the total accommodation capability curve and load time series characteristics are used to obtain the accommodation capacity by time distribution. Secondly, on this basis, three penetration limit values of power, capacity and energy are defined. The penetration limit values are defined as the maximum value of penetration under the condition that the DG output does not exceed the accommodation capacity at any time. Thirdly, the calculation method of the penetration limit values are given. The DG capacity limit value is determined according to the DG capacity, its time series output characteristics and the accommodation capacity by time distribution, then the penetration limit values are obtained. Finally, an IEEE 33 node example is used to verify and compare with the existing penetration calculation methods, which proves the results in this paper are more accurate. The penetration limit value obtained in this paper is easy to use, which provides important reference indexes for measuring the degree of DG integrated to the distribution network on the premise of meeting the security requirements.