Abstract: In density logging with the controllable neutron source, the number of neutrons emitted by the pulsed neutron source fluctuates from pulse to pulse, which leads to the poor accuracy of the density measurement results under the impact of different formation and detecting conditions. In order to improve the stability and accuracy of the density measurement, a density algorithm suitable for the developed integrated logging instrument with the controllable neutron source was established in this study. Firstly, the modeling of the new integrated logging instrument and the formation was carried out with the Monte-Carlo numerical simulation software MCNP. Then, the interaction process between fast neutrons emitted from the D-T neutron source and formation materials under different lithology and porosity conditions was simulated using the built model. By recording the near and far inelastic scattering γ-ray counts and capture γ-ray counts, near thermal neutrons and near epithermal neutrons counts from neutron detectors, the response relationships between the detector count of the integrated logging instrument and formation density were obtained, and the main factors which affect the density algorithm were also analyzed. Finally, based on the analysis of the density response characteristics, a new algorithm for controllable neutron source density logging which uses the ratio of near thermal neutron counts and near epithermal neutron counts and the ratio of near and far inelastic γ-ray counts was proposed to improve stability and accuracy. The calculation results show that the calculated density of sandstone, limestone and dolomite is very close to the true density, and the relative error is less than 6%. Compared with the calculation results of Halliburton and Schlumberger algorithms, the method in this paper shows better results of less formula parameters, no detector absolute counting, and high accuracy.