Exploring the physiological response to drought, to screen drought-resistant varieties, accelerate the breeding of drought-resistant Phalaenopsis varieties, meet the market demand in arid areas, and improve economic benefits.

Eleven Phalaenopsis cultivars were selected, and their photosynthetic parameters, chlorophyll fluorescence characteristics and physiological indexes were investigated after natural drought following watering, and the drought-resistant varieties were screened out by using membership functions and cluster analysis.

As the water content decreases, the net photosynthetic rate, chlorophyll fluorescence parameters, and chlorophyll content of most varieties continuously decline, while the intercellular CO₂ concentration, electrical conductivity, soluble sugar content, and malondialdehyde content continuously increase. The contents of CAT, SOD, and soluble proteins show a trend of first increasing and then decreasing. The drought tolerance evaluation system constructed based on the membership function method indicates that the drought tolerance ranking of the varieties is as follows: ‘Gold Princess’ > ‘Dior’ > ‘Sunrise’ > ‘Aurea Mocha’ > ‘Las Vegas’ > ‘Anna’ > ‘Prince Berry’ > ‘Bordeaux’ > ‘Gongxi Facai’ > ‘Man Tianhong’ > ‘Dream Lady’. Through cluster analysis, the 11 Phalaenopsis varieties are divided into two categories based on their drought tolerance. The first category consists of six drought-tolerant varieties, namely ‘Gold Princess’ ‘Dior’ ‘Sunrise’ ‘Aurea Mocha’ ‘Las Vegas’ and ‘Anna’, the second category includes five general varieties, namely ‘Prince Berry’ ‘Bordeaux’ ‘Gongxi Facai’ ‘Man Tianhong’ and ‘Dream Lady’.

‘Gold Princess’ ‘Dior’ ‘Sunrise’ ‘Aurea Mocha’ ‘Las Vegas’ and ‘Anna’ can adapt to the dry climate of Ningxia and are suitable for planting and popularizing in Ningxia; ‘Prince Berry’ ‘Bordeaux’ ‘Gongxi Facai’ ‘Man Tianhong’ and ‘Dream Lady’ may need frequent watering in the arid area of Ningxia and the cost is high, so they should be planted appropriately.