In order to synchronize the elements of the EAST Neutral Beam Injector(NBI)spatially located in several places,a distributed Timing System(TS) is developed in this paper.The timing system provides a clock reference for synchronization and an interlock protection of the EAST NBI system.It sends timing signals to field devices,controls the pulse widths of the timing sequences,and provides a sampling clock for the Data Acquisition System(DAS).The timing system also generates analog waveforms to control power supplies and gas supplies according to the operator’s configuration.The timing system is developed on a PXI(PCI extensions for Instrumentation) platform consisting of a Lab VIEW workstation and a timing control terminal.The timing control terminal consists of a timing node and several control interface crates.Two timing nodes are configured in one beam line.Each node is responsible for the timing sequence,analog generation and feedback control for one ion source.The architecture and implementation of the timing system are presented in this paper. In order to synchronize the elements of the EAST Neutral Beam Injector (NBI) spatially located in several places, a distributed Timing System (TS) is developed in this paper. Timing system provides a clock reference for synchronization and an interlock protection of the EAST NBI system .It sends timing signals to field devices, controls the pulse widths of the timing sequences, and provides a sampling clock for the Data Acquisition System (DAS). The timing system also represents analog waveforms to control power supplies and gas supplies according to the operator’s configuration. The timing system is developed on a PXI (PCI extensions for Instrumentation) platform consisting of a Lab VIEW workstation and a timing control terminal. The timing control terminal consists of a timing node and several control interface crates. Two timing nodes are configured in one beam line. Each node is responsible for the timing sequence, analog generation and feedback control for one ion source. The architecture and i mplementation of the timing system are presented in this paper.