The environmental pollution, property losses and casualties caused by wildfires in California are getting worse by the year. To minimize the interference of wildfires on economic and social development , and formulate targeted mitigation strategies, it is imperative to understand the scale and extent of previous wildfire occurrences. In this study, we studied the trend of wildfires in different time scales (monthly, seasonal, and yearly), as well as the distribution of wildfires caused by natural and anthropogenic factors across different spatial scales (administrative units, land use) in California from 2000 to 2019. Furthermore, a regression analysis of environmental and human-related variables with the occurrence and frequency of wildfires was carried out, to compare the importance of variables on the risk of wildfire occurrence. The results show that the frequency distribution of the burned area conforms to the characteristics of the Pareto distribution in the twenty years of this research. The spatial distribution of wildfires was closely related to factors such as the causes, population density, and land-use types. In terms of the variables related to the risk of wildfire occurrence, distance to human constructions, the elevation of the terrain, grass cover, and the vapor pressure deficit are crucial. This study reveals the relationship between environmental and social background conditions and the spatial-temporal distribution of wildfires, which can provide a reference for wildfire management, the formulation of future targeted wildfire emergency plans, and the planning of future land use in California.