Abstract: The investigations on the maion ecological factors and insect and disease status in mixed and monocultured stands of Pinus armandii growing under the same site conditions were made.The results were systematically analyzed in line with the theories of ecology,biology and forest protection.The data showed that mixed stand of P.armandii had richer biodiversity than that of monocultured stand in terms of underlayer plant species,which caused the differences between two stands in the aspects of temperature,moisture,soil properties,distribution of flora and fauna and species of insects in the system.