Aiming at the impact of amplitude domain feature analysis, characteristic extraction and characterization, and dynamic signal modelling of complex dynamic electricity signals on electricity metering, Firstly, a stochastic parameter model for complex dynamic electricity signals is developed to extract the amplitude of high-speed railway complex dynamic electricity signals. Secondly, a stochastic signal modulation model is deduced in amplitude domain, and some functions representing four important global characteristics of current amplitude are constructed. Thirdly, a multi-characteristic constrained model and constraints are proposed to represent global characteristics of complex dynamic electricity signals under actual operating conditions. Finally, a long m-sequence test signal model and constraints are constructed under experimental conditions to represent the important global characteristics of laboratory test signals in real conditions. Furthermore, a physical experiment is designed to validate the practical value of the important global characteristics and shows that the probability density distribution, variance, expectation and statistical modulation coefficient of current amplitude led to dynamic errors ranging from -5.94% to -9.72%.