Abstract: To identify the characteristics of greenhouse soil ammonia volatilization and the effect of nitrogen application reducing on ammonia volatilization loss and cucumber yield, a study was carried out with three nitrogen treatments (urea) under conventional irrigation conditions. Also the ammonia volatilization rates were measured in cucumber field with venting method in the winter and spring. The results showed that the peaks of ammonia volatilization rates appeared at seventh day after applying basal fertilizer. After topdressing, the peaks of ammonia volatilization rates in fertilization and non-fertilization zone appeared at the first day and fifth day, respectively. Compared with the basal fertilizer, the peaks value decreased from 8.6% to 46.3%. Ammonia volatilization accumulation in fertilization zone was 0.91-1.54 times of that of non-fertilization zone. Ammonia volatilization loss changed from 16.7 to 26.6 kg/hm2 in cucumber field in the winter and spring. Compared with conventional N rate treatment N1200 (1 200 kg/hm2), the ammonia volatilization loss of the treatments which reduced by 25% (900 kg/hm2) and by 50% (600 kg/hm2) of nitrogen application decreased by 22.1% and 37.2% respectively. The average cucumber yield of N600 treatment (600 kg/hm2) was highest in two years and it was 6.25% higher than that of N1200 treatment (1 200 kg/hm2). Based on general combining the ammonia volatilization loss, with cucumber yield and with nitrogen application in greenhouse in Hebei Province, it is feasible that the N rate decreases by 25% (900 kg/hm2) to 50% (600 kg/hm2) compared with conventional N rate (1 200 kg/hm2).