PM2.5 is the main pollutant affecting the air quality,the concentration of PM2.5 is closed related to meteorological conditions,studying the influence of meteorological conditions on the concentration of PM2.5 has important significance for improving urban air quality.As fractal and wavelet have lots of advantages when dealing with complex nonlinear system,the calculating method of joint multifractal based on wavelet packet transform modulus maxima(WPTMM) has been proposed,first the variable sequences are d...