Complex reservoirs usually have characteristics such as strong heterogeneity，large lithological changes，and complex pore structures. Traditional single frequency or narrow spectrum inversion methods are difficult to accurately describe reservoir characteristics. However，the low-frequency part retains richer information reflectingthe underground interface in actual seismic data，which plays an important role in the fidelity of inversion results. Especially with the improvement of seismic acquisition accuracy，the low-frequency information contained in earthquakes is becoming increasingly rich. In inversion，it is necessary to fully explore and utilize low-frequency information to improve the accuracy of reservoir prediction. Therefore，based on the understanding of sedimentary laws and geological structures as geological information，research on broadband spectrum inversion techniques with geological constraints was carried out. A geological model was designed based on the lithological combination of a single well，and a broadband wavelet that conformed to seismic data was constructed for forward modeling. The impact of low-frequency information on inversion and the seismic reflection characteristics of complex lithologies were analyzed by comparing it with actual seismic data. A broadband wavelet for mining low-frequency information in seismic data was constructed，and a quantitative template for time thickness and bandwidth was established. Low-frequency constraint factors were added to the inversion objective function，and a broadband spectrum inversion technique based on geological low-frequency constraints was formed. Simulated annealing and improved least squares joint optimization algorithm were employed to achieve precise reservoir description of lithological oil and gas reservoirs. Theoretical model testing has verified the accuracy and effectiveness of the broadband spectrum simulation algorithm for complex reservoirs based on geological constraints. Practical application in the turbidite sand bodies of the Chaoyang-Yong’an area in the Fushan Sag has shown that the inversion results are in good agreement with actual logging data. The broadband spectrum simulation inversion for complex reservoirs based on geological constraints can well predict the longitudinal and transverse sand body distribution characteristics of each sand group in the upper submember of the second member of Liushagang Formation in the Chaoyang-Yong’an area，providing a basis and guarantee for well site deployment in this area.