The present disclosure provides an ionic gel film preparation method, a chemical sensor and preparation method thereof, relating to the field of sensor technology. The preparation method of ionic gel film includes: blending a vinyl-free ionic liquid with a vinyl-containing ionic liquid and a specified additive to obtain a homogenous solution, taking a predetermined amount of the homogenous solution and dropping it onto a first substrate equipped with interdigital electrodes, flattening the homogenous solution on the first substrate using a second substrate, curing the flattened homogenous solution on the first substrate using ultraviolet light of a preset wavelength, and curing until the vinyl-containing ionic liquid polymerizes in situ to form an ionic gel film. The preparation method of ionic gel film, chemical sensor, and preparation method thereof of the present disclosure have the advantages of good device consistency, high conductivity, and good sensing performance when using the ionic gel film.