Nuclear DNA amount is an important biological concept that includes DNA C-value and genome size. There are conflicting reports about latitudinal variation patterns of plant nuclear DNA amount. Relationships of plant nuclear DNA amount with latitude, altitude, and climatic variables have been reported as linear. Disputes also exist as to whether nuclear DNA amount of plants is of environmental adaptation significance. We speculated that the conflicting reports were due to insufficient sampling of the taxa, limitations in the geographical range, and different genetic backgrounds of the samples. Asteraceae is not only the largest family within angiosperms, but also a widely accepted natural taxa. To clarify the latitudinal variation patterns of plant nuclear DNA amount on a global scale, and to explore the possible climatic adaptation significance of these patterns, we conducted a study with Asteraceae to analyze the relationships of nuclear DNA amount with latitude and bioclimatic variables. First, we obtained the data of nuclear DNA amounts of 822 species of Asteraceae from the Plant DNA C-value database. We selected ten global longitudinal transects, each with a span of 15 longitudinal degrees, and evenly divided each transect(from 82.5°N to 82.5°S) into 22 blocks. We obtained geographical records of the 822 species from the Global Biodiversity Information Faculty, together with fourteen bioclimatic factors within these blocks from the Worldclim Global Climate Database. We calculated the average DNA 1C-values and genome sizes of each species in each block. To avoid multicollinearity among the fourteen climatic variables, we performed principal component analysis(PCA) to reduce the dimensionality of the variables. We found that the mean temperature of the coldest quarter and the precipitation of the driest quarter had the highest loads in the first two principal components. The climatic variables with low correlation coefficients(-0.7 to 0.7) with the above two variables were included in the analyses. We found that the nuclear DNA amounts of Asteraceae had a regular latitudinal variation that could be expressed by polynomial functions. The relationships of nuclear DNA amount with the mean temperature of the coldest quarter, the precipitation of the driest quarter, and the wettest month were typically nonlinear with a unimodal pattern, and could be expressed by binominal equations. Therefore, on the global scale, plant nuclear DNA amount changes regularly on latitudinal gradients, which has distinct climatic adaptation significance.