  Discrete-modulated continuous-variable quantum key distribution offers a
pragmatic solution, greatly simplifying experimental procedures while retaining
robust integration with classical optical communication. Theoretical analyses
have progressively validated the comprehensive security of this protocol,
paving the way for practical experimentation. However, imperfect source in
practical implementations introduce noise. The traditional approach is to
assume that eavesdroppers can control all of the source noise, which
overestimates the ability of eavesdroppers and underestimates secret key rate.
In fact, some parts of source noise are intrinsic and cannot be manipulated by
eavesdropper, so they can be seen as trusted noise. We tailor a trusted model
specifically for the discrete-modulated protocol and upgrade the security
analysis accordingly. Simulation results demonstrate that this approach
successfully mitigates negative impact of imperfect source on system
performance while maintaining security of the protocol. Furthermore, our method
can be used in conjunction with trusted detector noise model, effectively
reducing the influence of both source and detector noise in experimental setup.
This is a meaningful contribution to the practical deployment of
discrete-modulated continuous-variable quantum key distribution systems.
