The harmonic characteristics of appliance loads have made power quality problems in distribution system become increasingly prominent. Thus, the electricity principles and harmonic characteristics of typical appliance loads are elaborated in detail and simulated, in summary that appliance loads have cause the distribution system some power quality problems, such as excessive harmonic currents, neutral over-current; on this basis, power quality of typical residential loads in distribution system are tested by using power quality analyzer Fluke430Ⅱ, the field measurements show that harmonic currents in distribution system have exceeded the national standard. Finally, some improvement measurements are proposed to solve the power quality problems.