The invention relates to a 
digital signal modulation mode identification method, which comprises the following steps of: encoding an 
original data stream sequence of a transmitting end with a known modulation mode by utilizing a differential space-time encoding technology to obtain a 
code word sequence x (k), and estimating by utilizing autocorrelation matrixes J and x (k) to obtain a receiving 
signal sequence y (k); carrying out zero-forcing 
equalization technology 
processing on y (k) to obtain a received 
signal compensation matrix (shown in the specification), and calculating the received 
signal compensation matrix (shown in the specification) by utilizing different high-order cumulants (shown in the specification); and calculating the received signal compensation matrix (shown in the specification) by utilizing different high-order cumulants (shown in the specification). obtaining a received signal eigenvector matrix Cij according to the eigenvector of the received signal eigenvector matrix Cij and the eigenvector of the received signal eigenvector matrix Cij; And performing normalization 
processing on the Cij to obtain a normalized modulation mode 
feature vector CijF, and inputting the normalized modulation mode 
feature vector CijF and a 
deep learning network which is trained and built by the CijF and the category 
label pair. According to the 
system for identifying the modulation mode to be identified, a receiving signal sequence is collected at the receiving end of the 
system, a normalized modulation identification 
feature vector is obtained according to the method inthe above step and serves as the input of a trained classifier, the output of the classifier serves as the tag sequence of the 
system modulation mode, and modulation mode judgment is completed.