Phosphate (Pi) transporters play critical roles in Pi acquisition and homeostasis. However, currently little is known about these genes in oil crops. In this study, we aimed to characterize the five Pi transporter gene families (PHT1-5) in allotetraploid

Brassica napus

. We identified and characterized 81 putative PHT genes in

B. napus

(

BnaPHTs

), including 45 genes in PHT1 family (

BnaPHT1s

), four

BnaPHT2s

, 10

BnaPHT3s

, 13

BnaPHT4s

and nine

BnaPHT5s

. Phylogenetic analyses showed that the largest PHT1 family could be divided into two groups (Group I and II), while PHT4 may be classified into five, Groups I-V. Gene structure analysis revealed that the exon-intron pattern was conservative within the same family or group. The sequence characteristics of these five families were quite different, which may contribute to their functional divergence. Transcription factor (TF) binding network analyses identified many potential TF binding sites in the promoter regions of candidates, implying their possible regulating patterns. Collinearity analysis demonstrated that most

BnaPHTs

were derived from an allopolyploidization event (~40.7%) between

Brassica rapa

and

Brassica oleracea 

ancestors, and small-scale segmental duplication events (~39.5%) in the descendant. RNA-Seq analyses proved that many

BnaPHTs

were preferentially expressed in leaf and flower tissues. The expression profiles of most colinearity-pairs in

B. napus

are highly correlated, implying functional redundancy, while a few pairs may have undergone neo-functionalization or sub-functionalization during evolution. The expression levels of many

BnaPHTs

tend to be up-regulated by diifferent hormones inductions, especially for IAA, ABA and 6-BA treatments. qRT-PCR assay demonstrated that six

BnaPHT1s

(

BnaPHT1.11

,

BnaPHT1.14

,

BnaPHT1.20

,

BnaPHT1.35

,

BnaPHT1.41

,

BnaPHT1.44

) were significantly up-regulated under low- and/or rich- Pi conditions in

B. napus

roots.