The objective of this research is to study socio-economic conditions and way of life of the Hmong which affected the degradation of natural resource and environment, and to find out the relationships between their behaviour on natural resource conservation and other independent factors such as ages; educational levels; number of family members; economic status; land use; land holding; expectation of children’s education; facility devices and their knowledge of soil/water/forest conservation as well as the usage of chemical substance. The sample of the population in this research is the Hmong in Mae Cham district, Chiang Mai province. One hundred and twenty samples are selected by simple random sampling technique. Questionnaires, observation of behaviour and way of life are used to collect data. The data is analyzed by means of descriptive statistics and inferential statistics such as percentage, frequency, means, deviation value, Speraman’s rank and Pearson in order to examine the relationships between independent factors and dependent factors. The research reveals that sample is found to be male as head of the family for 99.2% with an average of 40.45 years, and 49.2% of them have never been educated through any formal education system. Number of family members in average is 7.35 persons. 53.3% are poor, but expect to educate their children at least up to bachelor’s degree. 45.0% some properties such as chemical sprayer and pick-up truck. However, 83.8% does not have access to electricity. For their mode of production, 50.8% is found to have land use with average of 19.79 rai, while 73.3 % occupies land holding with 5.97% rai in average. Toward these lands 75.0% is found as inheritance, and 99.2% has received the land for more than 5 years. Most of their cultivating practices have been using rainfall. Fruit trees are planted for 44.2% and 90.0% of planting plots are set up vertically along the hill slope. 95.0% of planting period fall on March to August and weedicide have been used for 79.7%. Furthermore, 79.2% of the samples acknowledge the benefit of vetiver grass, and of forest for 93.9% and also knew that cutting trees for commercial purpose is illegal. 90.8% knows how to use water supply economically, while 95.8% knows that Cymbopagon citratus and Azadirachta indica are not harmful to the environment. For natural resource conservation behaviour, this research reveals that the Hmong’s behaviour in conserving soil/forest/water and chemical usage is very low, and it became a major cause of the degradation of natural resource and environment. Toward peaason’s testing, it is found that 1. there is a positive relationship between knowledge of soil conservation and the behaviour of soil conservation, 2. age level has negative relationship with the behaviour of forest conservation, 3. knowledge on forest conservation is positive relationship with forest conservation behaviour, 4. knowledge on water conservation has positive relationship with water conservation behaviour, and 5. knowledge on chemical usage has positive relationship with the behaviour of its usage. Toward Speraman’s rank testing, it is found that educational level has positive relationship with the behaviour of soil and forest conservation. This research suggests that the government or its concerned agencies especially the Highland Agricultural Extension Center, Chiang Mai Agricultural Extension Office, Department of Agricultural Extension and the Royal Project Foundation should pay more attention to nonformal education system. They should also try to develop infrastructure facilities particularly roads and electricity. These agencies should initiate training project and extend knowledge concerning the conservation of natural resources, environment, soil, water, forest and also how to use chemical substances appropriately. (p. Ngor-Chor)