The agricultural sector is going to face enormous challenges in order to feed the 9.6 billion people that the FAO predicts are going to inhabit the planet by 2050: food production must increase by 70% by 2050, and this has to be achieved. The advent of Internet of Things (IoT) that is the hot points in the Internet field has shown a new direction of innovative research in agricultural domain. Hence, in this research we seek to identify the applications of IoT in smart agriculture. This research is an applied research in nature and it would be classified as qualitative regarding data collection. In order to identify the usages of IoT in smart agriculture with the help of meta-synthesis approach, at first we have examined 480 researches among which only 168 have been selected for the final analysis, then we categorized them in 8 area of agriculture that consist of “farming”, “greenhouse”, “urban agriculture”, “Smart Gardening”, “smart fishery”, “smart forestry”, “smart livestock” and “smart supply and distribution network”. based on data analysis applications in 6 categories of “monitoring”, “control”, “tracing”, “diagnosis” and “descriptive planning” are categorized. Finally, agricultural area based on sustainable development indicators are respectively: smart greenhouse, smart supply and distributions network of agriculture, smart livestock, smart Gardening, smart fishery, smart farming, smart forestry and smart urban agriculture.