The temperature crack control of mass concrete is the key and difficulty in underground concrete structure engineer.In the underground structure of roll-over machine room of a port,the expansion reinforcing is applied instead of the post-cast strip.With the assistance of Midas civil software and ISDN mass concrete temperature monitoring system,the temperature and stress of the hopper concrete beam is monitored and analyzed.This method avoids the formation of concrete temperature crack and reduces the construction time.It also achieves excellent economic benefit.