To investigate the penetration mechanism of jacking closed pipe pile i n clay,a indoor model text was conducted.Two closed pipe piles of different di ameters were fabricated.The shallow-grooves of the piles were used to embed si x sensitized micro-fiber grating sensors in a single pile.The internal force va r iation of the piles in the static pile process was continuously monitored.The t est results show that:Due to the high sensitivity coefficient and long-term st a bility of the FBG sensing technology,it can better monitor the stress state of the pile during the pile sinking process.The larger the pile diameter is,the l arger the friction resistance ratio and the unit friction is,the smaller the en d resistance ratio is.The different axial forces of the two piles are decreasin g with the increase of the pile depth at different pile depths,but the pile of small deceleration rate is fast.