In order to predict the effect of changes in temperature, radiation and humic acid on wheat yield, a factorial experiment was used in a completely randomized block design with three replications in 2016-2017. Treatments included wheat cultivation in Back cross of Roshan cultivar in two types of clay-loam and loam-sandy soil (two locations) in four levels of humic acid spraying (0, 5, 10 and 15 gr/1000) in stem elongation. The results showed that by consuming 15 gr/1000 of humic acid per hectare in two types of soil, the highest yield (clay-loam and loam-sand, respectively, 7800.3 and 5270 kg / h) was produced. In the loam-sandy soil, the amount of proline and chlorophyll content of amino acids increased with increasing consumption of humic acid. Changes in photothermal ratio of booting stage to pollination in contrast to the amount of humic acid follow the second order equation. Humic acid consumption reduced the photothermal ratio, and this decrease as a result of consumption of humic acid had a positive effect on increasing the length of developmental stages. The grain yield per unit area corresponded to the photothermal ratio of booting stage to pollination from the second order equation. Humic acid increased the chlorophyll content (53.3 to 57.26 SPAD) and proline content of leaves (295 to 376.1 mg/kg leaf); thereby it caused the adjustment of thermal stress and increasing the length of the growing season. Clay-loamy soil produced higher grain yield than loam-sandy under both consumption and non-consumption of humic acid.