Previous literature on cause analyses of urban heat islands (UHI) lacks perspective from the combined effects of natural and humanity factors. With this prerequisite, the present study used Landsat TM/OLI remote sensing images to extract urban thermal fields of Fuzhou city, a typical valley basin in China, during 1991, 2000, and 2013. The combined effect and linkage relationship between the multidimensional factor and UHI was also explored using DMSP/OLS, traffic density, and land surface information indexes, including normalized difference building index (NDBI), digital elevation model (DEM), normalized difference vegetation index (NDVI), and modified normalized difference water index (MNDWI), based on GIS and principal component multiple regression. The results revealed that (1) the UHI of the Fuzhou valley basin has spread outward along the Minjiang River while the inner-city has become the core area of the UHI, commencing its significant overflow heat phenomenon from the center to outer edge from 1991; (2) the temperature difference between the plain and mountainous areas in the basin reached 10-14℃, and the UHI area displayed a polarization appearance indicating that both the low and high temperature areas have tendency to increase. Moreover, the high temperature area increased four times to 138.5 km² between 1991 and 2013, with an average annual growth rate of 7.5%; 3) according to the coefficient simulation, the basin temperature changed 0.430, 0.418, 0.103, -0.0310, -0.469, and -0.0963 as the night light intensity, NDBI, traffic density, NDVI, DEM, and MNDWI increased every 1 unit respectively; (4) the human promoting effect was greater than the natural inhibition on the UHI, resulting in the basin warming by 0.35 units; and (5) in comparison to the NDBI, night light intensity and traffic density contributed more significantly to the warming of the UHI, and the cooling effect of surface elevation is prominent, followed by water and surface vegetation, with these accounting for only 27% of the surface elevation effect. In addition, the cooling effect was obvious when the natural effect further increased by 60% and Fuzhou city simultaneously remains at the existing developmental scale. This also reveals that the current ecological environment of the Fuzhou basin is not enough to alleviate the UHI caused by future development of the city.