The invention discloses a method capable of simultaneously expanding multichannel decoding and multichannel intelligent video processing functions and a device thereof. Under the condition that hardware resource design of the original digital video recorder is not changed or less changed, a sub board provide with a plurality of DSP chips can be expanded by virtue of a PCI interface, so as to carry out multichannel decoding and multichannel intelligent video analysis.Maximum utilization factor of DSP on the expansion board is achieved by adopting the way that decoding function and intelligent analysis function of the expansion board are mutually switched, so that all the DSPs of the expansion board are used for one function in different operation states, thus increasing the number of channels supported by decoding and intelligent analysis. Hardware design implementation of the embodiment of the invention is simple, and an expanded common digital video recorder can simultaneously furthest support multichannel high resolution decoding function and multichannel video analysis processing function without adding other equipment.