The invention discloses a gamma
radiation source item inversion method and
system based on a regularized least square method. The method comprises the following steps of S1, carrying out area divisionon a gamma
radiation source item, wherein radioactivity in each source item division area is uniformly distributed in a space; S2, according to
dose rate measurement data at multiple external measurement positions and uncertainty, and the
dose rate contribution of the unit radioactivity of each source item division area to each measurement position, through an
optimization problem, determining atarget function used for calculating a radioactivity value in each source item division area; and S3, calculating the target function and acquiring the radioactivity value in each source item divisionarea. By using the method and the
system of the invention, based on a given source item division mode and a
nuclide type, according to measured data and a
dose rate contribution matrix, through a regularized least square principle, gamma
radiation source item activity data which is relatively stable and matches with the accuracy of the measured data is inverted.