From investigation in the field

it has been discovered that a big systematic error existing in coal sampling for quality control of plant -incoming coal.After analysis of the causes

some improving methods have been put forward as follows:(1)changing the sampling depth from 0.4m to 0.6m;(2)setting the mass of subsample to be≥7.5 kg in case the particle size of plant-incoming coal to be≥100mm. After adopting said methods

systematic error of measuring the total moisture content to be-0.1%

and no systematic error occurred in measuring the high calorific value.The said methods can provide reference for revising related satandards.