Totally 56 kinds of volatile organic compounds (VOCs) in ambient air of Ji'nan City in summer 2010 were monitored by online GC to analyze their pollution characteristics and their relationship with weather conditions. The results showed that the majority of VOCs in ambient air in Ji'nan were alkanes, aromatics and olefins, accounting for 98.2% of the 56 kinds of total volatile organic compounds (TVOCs) detected. The concentrations of VOCs remained stable in June and July, and were significantly higher in mid and late August, and the quality percentages of the VOCs components showed some variations with changes in temperature. In sunny days, the diurnal variation curve of VOCs concentration had a bimodal characteristic, with the two peaks appearing in the rush hours with heavy traffic. There were no obvious bimodal distribution in rainy days and the concentrations were higher. The concentration of VOCs in ambient air in summer showed negative correlation with the wind speed and hours of sunshine, when the atmospheric stability was high, the pollutants were difficult to diffuse, which lead to increasing concentration of VOCs. The main sources of VOCs in Ji'nan are industrial emissions, motor vehicle emissions, the evaporation and leakage of gasoline, etc.