A detection method, a surface density device (100), a detection means (200), and a storage medium are provided. The surface density device (100) includes a radiation source (10) and an ionization chamber (20) spaced from the radiation source (10). The detection method includes: obtaining, during operation of the surface density device, a first current pose of the radiation source (10) and a second current pose of the ionization chamber (20); determining a first pose deviation of the radiation source (10) based on the first current pose; determining a second pose deviation of the ionization chamber (20) based on the second current pose; and determining whether the radiation source (10) has undergone a pose change with respect to the ionization chamber (20) based on the first pose deviation and the second pose deviation.