Time-domain fractional differentiation of seismic signals is a signal processing method in the field of differentiation. Compared with the traditional integer order differential processing and frequency domain seismic signal extension methods, the multi-scale characteristics of seismic signals can be better described and the data reliability can be improved. In order to deal with complex seismic signals with narrow frequency bands and obtain more refined seismic data, this paper proposes a seismic data extension method based on multi-level fractional differential adaptive fusion in time domain, which automatically obtains the weighted fusion coefficient by using the method of adaptive dynamic adjustment of the weighted coefficient according to the characteristics of fractional differential signals in different frequency bands in different frequency bands and the envelope of the spectrum of differentially differentiated signals of different orders. The seismic signal after frequency extension processing effectively reduces the influence of seismic wavelet band limiting. The model test and practical application show that the fractional differential operation in the time domain of the seismic signal highlights the high-frequency component of the original seismic signal and maintains the low-frequency component of the original signal. With the increase of the differential order, the main frequency of the differential signal increases, and the number of sidelobes increases while the width of the sidelobes narrows, and the ratio of the sidelobe value to the mainlobe value also increases gradually. After multi-level fractional differential adaptive fusion processing, the sidelobe amplitude can be effectively suppressed, the frequency band range can be broadened, and the ability to explain and characterize the reservoir can be provided more clearly, which can improve the ability to identify thin interbeds to a certain extent.