Numerical solution of the unsteady natural convection from single and double heated cylinders places in a two-dimensional square enclosure with the cold isotherm walls is reported in this investigation. A square enclosure of equal length and width (L) that contains vertical cylinders with same radius R (=0.1L) situated in the vertical center line of enclosure length and separated by a distance (D). Rayleigh number varied from 10³ to 10⁷ of single and double heated cylinders and the effect of cylinders distance (D) was studied numerically. Rayleigh number is varied from 10³ to 10⁷ and the effect of double heated circular cylinders to single one and different distance of the cylinders located vertical of cavity are studied. The results show that the streamlines and isothermals strongly depend on Rayleigh number, which determined the heat transfer mechanism, when Ra=10⁷ asymmetric observed. When placed double cylinders in the cavity, it have little effect on the lower cylinder, but to the upper one the heat transfer and flow were strongly influenced by the lower one. It also found that when D/L=0.3 can get a better heat transfer effect. The distribution of streamlines, isothermals and Nusselt number are presented.