The gas-particle two-phase jet from a slit nozzle is numerically simulated by using a two-dimensional vortex method, which has been proposed for particle-laden free turbulent flow by the authors, to demonstrate the applicability of the method for two-phase jets. The method can take account of the interaction between the two phases by calculating the motion of particles and the behavior of gas vortex elements through the Lagrangian approach. The gas flow Reynolds number is 10000, and spherical glass particles having diameter of 65 gm are loaded with a mass loading ratio of 0.6. The mean velocities and turbulent intensities of the two phases are in good agreement with experimental results in the literature. The effects of particle on the velocity decay and momentum diffusion of the gas-phase jet are also favorably compared with measurements. These indeed indicate the applicability of the vortex method to plane gas-particle two-phase jets.