In order to find out suitable potassium(K)fertilizer application rates in improving lodging resistance in hilly area of central Sichuan basin，a field experiment was conducted in 2013 and 2014，a single factor randomized block design was adopted and five K fertilizer application rates(K2O5)were set up，including 0，45，90，135，180 kg·hm-2. The matter accumulation characteristics，chemical composition and mechanical indexes of basal internode in silking stage and filling stage，lodging rate and grain yield were measured. The results showed that the yield of spring maize increased by 1.19%-8.43%(2013)and 1.75%-9.19%(2014)；and the lodging rate decreased by 11.11%-44.44%(2013)and 12.50%-52.10%(2014)，compared with no K fertilizer input treatment. The lodging rate of maize was significant negative correlated with rind penetration strength，stalk crushing strength and stalk breaking strength of the second to the fifth internode at basal in silking stage and filling stage，fresh weight and fresh density of the second and the third internodes at basal in silking stage，and K content of the second to the fifth internode at basal in filling stage；while significant positive correlated with the content of soluble sugar and starch in the second to the fifth internode at basal in filling stage. The fresh matter weight and dry matter weight of the second to the fifth internode at basal of maize stalk were increased by applying K fertilizer. With the increase of K fertilizer application，the cellulose content，stalk breaking strength，rind penetration strength，and stalk crushing strength of the second to the fifth internode at basal showed a trend of increase first and then decrease，and the highest value was got under the treatment that K fertilizer application rate was 90 kg·hm-2. In summary，under the K fertilizer application rate of 95.0 kg·hm-2 to 121.0 kg·hm-2，the lodging resistance of plants were increased with the increase of cellulose content，stalk breaking strength，rind penetration strength，and stalk crushing strength of the basal internode，which resulted in much lower lodging rate and higher yield finally. This study could provide both theoretical and practical basis for lodging resistant and high yield fertilization technology in spring maize production in hilly area of central Sichuan basin.