Abstract: Abstract: The extensive application of residual current protection device in rural low-voltage power grid plays an important role to avoid electric shock casualties and fire accident caused by the leakage. Malfunction and failure action often occur in online residual current protection device due to the irrelevant between the setting value of action current and electric shock current of organism. Many researchers conducted a number of breakthrough research on detection of leakage current and hardware architectures of residual current protection technology, which improved the technology performance of residual current operated protective device to some extent, but it could not overcome the low efficiency of correct delivery rate. There were no mature technology and products at home and abroad on detection and characteristics of the law for biological shock signal when the organism was in electrical shock, which could not meet the need of reliable power system under many complicated factors. In this paper, detection model of biological electric shock current was researched based on Hilbert-Huang transformation. Therefore, aiming at how to detect electric shock time and recognize current signal of the biological electric shock branch in residual current, residual current and electric current signal of organism electric shock were set for example, Hilbert-Huang transformation method was used to determine local amplitude of the IMF component with the largest correlation coefficient in the natural modal function of residual current when biological shock occurred, this local amplitude was 34.02 mA, which reached 0.99 correlation coefficient with the original signal, meanwhile, there was a similar law of changes of spectral characteristics between residual current and electric shock current transient process. Biological current signal were consisted of 5 IMF components and one residual component, which accounted for 60.64% of total samples. The IMF component with the biggest correlation coefficient has much bigger variation range of amplitude. In actual signal processing, mutations of high frequency IMF could be used to determine the biological shock time, and IMF component with high amplitude share and correlation coefficient could be used to extract current amplitude of electric shock branch. Hence, in this study, based on those results above, firstly, mutation characteristics of high frequency IMF component amplitude in biological current signal could be used as a criterion and judgment method for electric shock time, which could automatically identify the moment of failure and locate the calculation. Simulation of the actual data processing accuracy was 94.17%. Moreover, low frequency natural modal IMF component was extracted from residual current decomposition, which should be higher relevance and limited quantity. At last, method was established for detecting current amplitude of biological shock branch based on natural mode component of residual current through application of stepwise multiple linear regression method. Simulation result shows that the average relative error is 5.46%，which indicates that the method proposed in this paper has good potential rapid technique for developing a new generation-residual current protection device based on biological electric shock current and plays an important role to avoid personal electric shock casualties and electrical fire in as well as safe operation low voltage power grid.