The invention discloses a method for predicting bathing habits and a water heater. The method for predicting the bathing habits comprises the following steps that S1, a controller acquires water usagerecords of the preset number of days acquired by a water flow sensor and a water outlet temperature sensor; S2, the controller determines the preset number N of Dayrulers, namely Dayruler1 to DayrulerN, and each Dayruler is assigned according to the selection mode of each Dayruler and the water usage records of the preset number of days so as to obtain Dayruler data, wherein N is a positive integer; S3, the controller determines a target Dayruler from the preset number of Dayrulers according to the Dayruler data; and S4, the controller determines the next water usage condition according to the target Dayruler. According to the method and the water heater, in this way, the water usage records of the preset number of days can be recorded, the different Dayrulers are assigned according to the water usage records of the preset number of days and the corresponding selection mode, then the water usage habits of users are determined according to the assigned Dayruler value, the bathing behavior is predicted according to the water usage habits of the users, and hot water is prepared for the users in advance according to the bathing behavior.