Bank of China Q4 profit drops less than expected on higher interest income

* BoC 2017 net profit up about 5 pct y/y

* NIM 1.84 pct vs 1.83 pct in 2016

* NPL ratio 1.45 pct vs 1.41 pct end-Sept (Adds interest income, other details)

SHANGHAI/BEIJING, March 29 (Reuters) - Bank of China Ltd (BoC) , the country's fourth-largest lender by assets, reported a smaller-than-expected drop in quarterly profit, helped by rising interest income and falling operating expenses.

Profit reached 26.9 billion yuan ($4.28 billion) for the quarter ended December, down 10 percent from 29.8 billion yuan a year ago. This was, however, better than an average estimate of 25.51 billion yuan from 18 analysts polled by Thomson Reuters.

For 2017, net profit rose about 5 percent to 172.41 billion yuan from 164.578 billion yuan a year ago.

BoC's non-performing loan ratio was 1.45 percent as at end-December, from 1.41 percent at end-September.

Its operating expenses fell 0.69 percent from a year ago to 173.86 billion yuan in 2017, while net interest income rose 10.57 percent to 338.39 billion yuan over the period.

BoC's net interest margins (NIM) - the difference between interest paid and earned by banks - was reported at 1.84 percent for 2017, versus 1.83 percent for the year ago. ($1 = 6.2888 Chinese yuan) (Reporting by Engen Tham in SHANGHAI and Matthew Miller in BEIJING; Editing by Himani Sarkar)