The invention provides a clock synchronization detection method and device for a circuit emulation service, and the method comprises the steps: obtaining first CES data and second CES data in a network, wherein the first CES data is data which does not enter the jitter cache of a destination end of a PSN, and the second CES data is the data which is outputted by the jitter cache of the destination end of the PSN; and detecting whether the clock frequency of the first CES data and the clock frequency of the second CES data are synchronized or not. The method determines whether the CES clocks are synchronized or not through comparing the clock frequencies of the data before jitter caching of the destination end of the PSN, can quickly detect whether the two-end clocks of CES data are synchronized or not, finds a problem in advance, and reduces the subsequent processing cost.