A study was caried out to examine the effect of post-harvest treatment with 1-methylcyclopropene on avocado fruits in storage. The avocado fruits (Persea americana Mill.) at 20 weeks after flowering were harvested from orchard in Kam Leo, Thang Hoa, Dak Lak province in year 2011. The quality of avocado fruits was identified in terms of the firmness at 35.50 kg/cm2. Total sugar content of 7.20 percent, total acid content of 0.05 percent, vitamin C content of 68 mg percent. The avocado samples were exposed with 1-MCP at the concentrations: 300ppm, 400ppm, 500ppm
600ppm, 700ppm during the time of 12,15,18,21,24 hours, then kept at ambient temperature (25 to 30°C
RH of 85 to 90 percent). Research results of single factors show that the quality of avocado fruits exposured with 1-MCP at the concentration of 500ppm during 12 hours is the best, which has weight losses lower than 10 percent compared with other samples after 12-day storage. Research results of multi-factor show that weight loss is lowest after 12 day storage when the concentration of 1-MCP for preserving avocado is 500 ppm and the time of 1-MCP treatment is 13hours 30mins.