The invention discloses a method for preventing duct piece displacement in the no-load shield tunneling process. The method comprises the following steps that (a) a through hole is formed in a duct piece; (b) a single inlet channel bag-shaped body is plugged into a gap from the through hole; (c) the bag-shaped body is filled with cement slurry by using a grouting machine, and the bag-shaped body expands and is in contact with the duct piece and a preliminary bracing system; (d) after grouting is completed, an inlet channel and the grouting machine are separated; (e) the cement slurry solidifies for forming. By applying the method, the bag-shaped body is plugged into the gap between the duct piece and the preliminary bracing system and is filled with the cement slurry to be supported between the duct piece and the preliminary bracing system and play a duct piece limiting and supporting role. The method is simple in process and good in operability, the consumed working time is short, the cost is low, an implementation effect is good, a hoisting hole or a grouting ole can be closed after implementation, follow-up work is omitted, and popularization is promoted.