Source from Wikitravel,
From Urumuqi, China从乌鲁木齐

The N895 train leaves every Saturday and Monday night (23:58 Beijing time) direct to Almaty. To buy the ticket in Urumuqi the office is in the Yaou Hotel to the right of the main station. Tickets need to purchased a few days in advance and cost around ¥870 (about US$110).

N895次国际列车每周六及周一晚上(北京时间23:58)从乌鲁木齐开往阿拉木图。 在乌鲁木齐的购票地点为乌鲁木齐火车南站右侧的亚欧宾馆, 应提前几天订票,票价为870元。

Ticket sale for the Saturday train starts on Monday 10am, for the Monday train it starts Friday 10am. The train on Saturday is very busy, while for the train on Monday it is possible to purchase the ticket on the same day. There will always bee free seats in the train so you may enter the train directly at the Chinese side of the border after buying the ticket there the same day .

从周一早上10点开始出售周六的火车票,从周五早上10点开始出售周一的火车票。 周六的火车票比较紧张, 而周一的火车票一般当天就可购得。一般火车上总会有空位, 所以在当天购得车票后上车都能找到位置。

The trip takes 34 hours, eight of which are spent clearing Chinese and Kazakh immigration.