In order to ensure the efficiency of response and disposal and reduce the damage caused by the hazardous gas leaks，it was necessary to quickly and accurately trace the location of the leak point as well as the source strength. In this article，a method of hazard location and source strength determination based on a complex algorithm was proposed. The basis of the algorithm was to compare the difference between the concentration of the monitored gas and the concentration calculated by the atmospheric diffusion model，and take the difference as the objective function，so that the parameter with the smallest objective function value was the optimal result of the source intensity and position. The results show that the complex algorithm can quickly and accurately obtain the location and source strength of the leakage source. Compared with the traditional simplex method，the compound algorithm has no restriction on the selection of initial value. Even if the selected initial value has a large deviation from the true value，the position and intensity of the source can be quickly obtained through the iteration of the complex algorithm，avoiding the shortcoming of the traditional simplex method，which has high requirements on the selection of initial value. A comparison of particle swarm optimization，genetic algorithm，simplex and complex algorithm is made in three aspects: traceability efficiency，traceability accuracy and traceability stability，which depicts that the complex algorithm is progressive. The complex algorithm can be applied to trace sources and determine source strength for continuous and instantaneous releases.