Urban agriculture （UA） in less developed countries （LDCs） is different from that in developed countries in their causes and trends. Many interests have been in researches of UA in LDCs in recent years. Based on these studies, this paper summarized the types and characteristics of UA in LDCs. The positive and negative effects were elucidated and also the impediments due to its negative effects. The corresponding research activities were introduced. In the last part the necessity of developing UA in LDCs was pointed out and the measures to regulate its development were discussed in detail.