In order to overcome the disadvantages of the traditional wired monitoring system in greenhouse, such as high cost, difficult movement, and difficult installation and maintenance, a wireless monitoring system in greenhouse was designed based on IEEE802.15.4. The self-organized star network was built by sensor (control) nodes and mobile sink nodes through dynamically constructing short-distance network. This design reduced the sensor (control) nodes energy consumption and prolonged the longevity of sensor network. The communication between monitoring center and sink nodes was accomplished by multiple steps. Information could be transmitted in time, safely and smoothly, which were guaranteed by the logical and effective time slot arrangement. The system, which has MSP430 and CC2420 hard-core parts, could intelligently monitor parameters in greenhouse wirelessly, such as temperature, humidity, light-intensity and so on.