In order to probe into the causes of relatively low gold content in samples rich in organic matter from forest-swamp areas of Northeast China, the authors used AAS analysis with aqua regia solution method and AAS analysis with tetracid solution method to determine Au content of samples. The application of the tetracid solution method to eliminating silica gel can obviously raise the determination value of gold. For samples with gold content higher than 10~(-9), the difference between the two methods are especially evident. The above investigation shows that gold in samples rich in organic matter from forest-swamp areas can exist not only in the form of organic combination but also in the colloid or nanometer form. Wrapped by SiO2 colloid, gold can migrate for a long distance in water solution in an active form under the protection of high-concentration organic acid. Nevertheless, the aqua regia solution method fails to determine such SiO2 colloid-wrapped gold.