With the increasing access for distributed energy and the enlarging demand for energy utilization, considering the difference of the electric/heating/cooling energy flow in multi-energy complementary park and the uncertainty of the distributed energy output, an evaluation method of the energy supply system in multi-energy complementary park based on the improved universal generating function (UGF) method is proposed. In this method, the constraints of the startup and shutdown and the climbing of conventional energy supply units are taking into account, and a timing UGF model of each energy supply unit in multi-energy complementary park which contains the wind turbine, photovoltaic, conventional unit, micro gas turbine, gas boiler and energy storage device is established. What's more, considering the reliability, economy and electrothermal coupling characteristics of the energy supply system, an evaluation index system of the energy supply system in multi-energy complementary park is built. Finally, the correctness and feasibility of the proposed evaluation method are verified through the typical IEEE-RTS79 system. In addition, taking a multi-energy complementary park in northern China as an example, the probabilistic production simulation (PPS) and sensitivity analysis for typical scenarios to achieve the overall evaluation of the energy supply system in the multi-energy complementary park are carried out.