The embodiment of the invention provides a turbine low-pressure cylinder flow determination method and device and a machine readable storage medium, and belongs to the field of steam turbine steam flow soft measurement. The method comprises: determining a training value set of auxiliary variables and a sample value set of the low-pressure cylinder flow, and the auxiliary variables comprising the following parameters: the unit load, the main steam flow, the main steam pressure and the medium-pressure cylinder steam exhaust pressure; obtaining a monitoring value of the auxiliary variable; basedon the training value set of the auxiliary variables and the sample value set of the low-pressure cylinder flow, training a neural network model; and determining the monitoring value of the low-pressure cylinder flow based on the monitoring value of the auxiliary variable and the neural network model obtained through training. Therefore, the low-pressure cylinder flow is simply calculated, the engineering application is facilitated, the fault-tolerant rate is improved, and the influence of wrong data is reduced.