An insertion module adapted to guide an insertion needle to move stably before inserting into a host, characterized by : a main body having an accommodating hole extending along an axial line (L), and a plurality of slide grooves disposed on said accommodating hole around the axial line (L) and communicating with said accommodating hole ; an auxiliary insertion seat having a base portion , and a plurality of wing portions connected to said base portion , wherein each of said wing portions is reciprocated within a respective one of said slide grooves , and has a protruding portion ; an insertion needle assembly including a needle seat assembled with said base portion of said auxiliary insertion seat , and an insertion needle connected to said needle seat , wherein a distance between a tip end of said insertion needle and a skin surface of the host is defined as an initial stroke distance (H); and a sensor assembly including a sensing seat , and a sensor held within said sensing seat , wherein said sensing seat is assembled with said base portion of said auxiliary insertion seat , and said insertion needle is inserted through said sensing seat to cover said sensor ; wherein each of said slide grooves has a wall surface , and said protruding portion of each of said wing portions resiliently abuts against said wall surface of a respective one of said slide grooves in point-contact such that said auxiliary insertion seat is fixed before inserting into the host through the interference between said protruding portions and said wall surfaces to provide a stable inserting and prevent said insertion needle from oblique in said initial stroke distance; and characterized in that said wall surface of each of said slide grooves is gradually widened along an insertion direction (F). a main body having an accommodating hole extending along an axial line (L), and a plurality of slide grooves disposed on said accommodating hole around the axial line (L) and communicating with said accommodating hole ; an auxiliary insertion seat having a base portion , and a plurality of wing portions connected to said base portion , wherein each of said wing portions is reciprocated within a respective one of said slide grooves , and has a protruding portion ; an insertion needle assembly including a needle seat assembled with said base portion of said auxiliary insertion seat , and an insertion needle connected to said needle seat , wherein a distance between a tip end of said insertion needle and a skin surface of the host is defined as an initial stroke distance (H); and a sensor assembly including a sensing seat , and a sensor held within said sensing seat , wherein said sensing seat is assembled with said base portion of said auxiliary insertion seat , and said insertion needle is inserted through said sensing seat to cover said sensor ; wherein each of said slide grooves has a wall surface , and said protruding portion of each of said wing portions resiliently abuts against said wall surface of a respective one of said slide grooves in point-contact such that said auxiliary insertion seat is fixed before inserting into the host through the interference between said protruding portions and said wall surfaces to provide a stable inserting and prevent said insertion needle from oblique in said initial stroke distance; and characterized in that said wall surface of each of said slide grooves is gradually widened along an insertion direction (F). <EOS>