Quantum metrology pursues high-precision measurements to physical quantities by using quantum resources. However, the decoherence generally hinders its performance. Previous work found that the metrology error tends to divergent in the long-encoding-time regime due to the Born-Markovian approximate decoherence, which is called no-go theorem of noisy quantum metrology. We here propose a Gaussian quantum metrology scheme using bimodal quantized optical fields as quantum probe. It achieves the precision of sub-Heisenberg limit in the ideal case. However, the Markovian decoherence causes the metrological error contributed from the center-of-mass mode of the probe to be divergent. A mechanism to remove this ostensible no-go theorem is found in the non-Markovian dynamics. Our result gives an efficient way to realize high-precision quantum metrology in practical continuous-variable systems.
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