The strain of pipe section of the immersed tunnel engineering in Zhejiang province is monitored by the fiber grating sensor. The sensor type selection, installation and on-site installation scheme are introduced. The testing data is analyzed and the section measured strain values of the measuring-point changing with time and the influence of tidal load on monitoring results are studied. The measured strain values are compared with the theoretical value according to the modified model for the theoretical calculation of the pipe strain. The results show that pipe strain stabled basically after the end of the year in the construction; and the strain regularity with time is related to the pipe location and the pipe ends joint; the tidal load impacts on pipe strain within the range of 0.8%-12%, and closely related to the joint form; when both ends of the pipe sections are flexible joints, the strain regularity and the tide level showing a strong correlation; correlation is not obvious when it is rigid joints; pipe strain theory calculated and measured values are close, with some reliability.