The invention discloses a drought propagation time calculation method based on conditional probability high spatial-temporal resolution, which comprises the following steps of: step 1, collecting specified rainfall data and soil humidity data, and processing the rainfall data and the soil humidity data into a ten-day scale sequence to obtain gridding rainfall data and soil humidity data with high spatial resolution; step 2, calculating a standardized rainfall index, and calculating a standardized soil humidity index; step 3, establishing joint distribution with an optimal dependency relationship between the standardized rainfall index and the standardized soil humidity index; and step 4, calculating the occurrence probability of agricultural drought caused under different levels of meteorological drought conditions, setting a threshold interval, and if the occurrence probability of the agricultural drought reaches a threshold value requirement, obtaining the propagation time from the meteorological drought to the agricultural drought. According to the method, the calculation precision of the drought propagation time is improved, and guidance can be provided for agricultural water resource management and agricultural drought prevention.