In order to reveal scale effects of relationships between corn ear weight and its affecting factors, the spatial variability of corn ear weight and its effect factors were firstly studied with geostatistics and multifractal methods, and then the relationships between corn ear weight and its affecting factors were analyzed at the multi-scale with joint multifractal. The results showed that corn ear weight had medium variation, variation degree of stem diameter changed from medium to weak variation with time, and other affecting factors of corn ear weight had weak variation;spatial correlation ranges of corn ear weight and its affecting factors were from 7.15m to 66.51m;spatial correlation degrees of corn ear weight, chlorophyll content, soil bulk density and volume fractal dimension of soil particle-size distribution were strong, and the ones of stem diameter, soil moisture and saturated soil moisture were medium;stem diameter and chlorophyll content had remarkable influences on spatial variability of corn ear weight at the single scale, and chlorophyll content, volume fractal dimension of soil particle-size distribution, stem diameter and soil moisture had noteworthy effects on its spatial variability at the multi-scale;most of correlation degrees of corn ear weight and its affecting factors at the multi-scale were more than corresponding ones at the single scale;at the single and multi-scale, as time changed, correlation degrees of corn ear weight and stem diameter were firstly increased and then decreased, but the times that the ones began to reduce were different. Multi-scale analysis could deeply and completely reveal correlations between corn ear weight and its affecting factors. The research results had great significance in revealing mechanism of spatial variability of corn ear weight, determining scale effects of relationships between corn ear weight and its affecting factors, guiding precision management of crop and soil and increasing crop production.