At present, taking trains from Fuzhou to Xiamen is rather inconvenient. Although the distance between the two cities is less than 300 kilometers, there are no direct rains and you need to transfer at midway. It will take about 12 hours to cover the distance. I heard that the government is now making a direct railroad between Fuzhou and Xiamen and the new one will be in operation in the end of this year probably. I suggest you to take a bus and it will just need about 4 hours.