The invention provides a field sampling device and a use method of filling slurry. The sampling device comprises a slurry cylinder control unit and a slurry cylinder, wherein the slurry cylinder control unit comprises a sampling rod, an upper transverse rod 5, and a lower transverse rod 12, and a control rod 15 is axially inserted into a main rod 3; the slurry cylinder comprises a slurry cylinder upper baffle 8, a slurry cylinder pipe 9 and a slurry cylinder lower baffle 11; and one end of the upper/lower transverse rod is fixedly connected with the control rod, and the other end of the upper/lower transverse rod is detachably connected with the slurry cylinder upper/lower baffle 8. According to the field sampling device and a sampling method of the filling slurry, the field sampling of the filling slurry is realized by driving the opening and the closing of the upper baffle 8 and the lower baffle 11 by the control rod of the slurry cylinder control unit; and the slurry at a fixed point can be precisely collected, the sampling can not be influenced by low-concentration filling slurry at the upper part of a collecting field in the rising processes of sampled samples, and the property of the filling slurry in the collecting field can be accurately acquired.