The invention is applicable to the technical field of distribution network planning and discloses a programming method and system for distributed photovoltaic grid-connected penetration level. The method includes the steps of determining photovoltaic power output and load output as random variables, and establishing a comprehensive probabilistic model of the photovoltaic power output and a probabilistic model of the load output; using Latin hypercube sampling method based on the principle of equal probability transformation and a square root method to generate mutually independent random vectors; determining a chance constrained programming model when the sum of penetration levels of distributed photovoltaic power supplies accessed to a distribution network system is the maximum, using a Cuckoo search algorithm based on a particle swarm algorithm to solve the chance constrained programming model, and obtaining the distributed photovoltaic grid-connected maximum penetration level; and according to the distributed photovoltaic grid-connected maximum penetration level, programming the photovoltaic grid-connected level of each node in the distribution network system. The method and system of the invention consider the characteristics of the randomness and volatility of the photovoltaic power output, improve the voltage distribution level of the nodes, and ensure the safe and stableoperation of the distribution network.