The performance of hydrocarbon R-290 and R-600a refrigerants as alternative to R-134a in vapor compression refrigeration, that is the split air conditioning system, the theoretically investigated the sub-cooling effect on the split air conditioning system. The effects of sub-cooling on the performance of the investigated refrigerants were quantified. The results obtained showed that the saturated vapour pressure and specific volume of R290 and R600a mixture are very close to those of R-134a; therefore, they had been used as substitute for R-134a.The condenser is performed better with these two refrigerant mixtures. The thermodynamic properties of (R-290/R-600a) mixture were obtained by using REPRPOP software. The coefficient of performance of investigated refrigerant mixture was found to be in range 3.08–3.35. The degree of sub-cooling greatly increased the coefficient of performance and it had the positive effects on  the refrigerating capacity.