  For decoherence processes induced by weak interactions with the environment,
a general quantum channel with one noise parameter has been formulated. This
channel is called low-noise channel and very useful for investigating the
parameter estimation in the leading order. In this paper, we formulate the
low-noise channel with multiple unknown parameters in order to address the
simultaneous achievability of the Cram{\'e}r-Rao bound for the parameters
estimation. In general, the simultaneous achievement of the Cram{\'e}r-Rao
bound for multi-parameter estimations suffers from non-commutativity of optimal
measurements for respective parameters. However, with certain exceptions, we
show that the Cram{\'e}r-Rao bound for output states of dissipative low-noise
channels can be always attained in the first order of the parameters as long as
D \leq N-1, where D and N denote the number of the parameters and the dimension
of the system, respectively. This condition is replaced by D \leq N^{2}-1 if it
is allowed to set the entanglement with ancilla systems in its input state and
to perform the non-local measurement on the composite system.
