This survey aims at studying the relationship between English vocabulary threshold and word guessing strategy that is used in reading comprehension learning among 80 pre-university Chinese students in Malaysia. T-test is the main statistical test for this research, and the collected data is analysed using SPSS. From the standard deviation test results, the large of vocabulary is proportional to the higher score of the reading test. The standard Pearson correlation coefficient of 0.750, and P< 0.01 indicated that there is a positive relationship between word guessing and vocabulary learning. T-test results showed that the vocabulary of the students should reach about 3500 words, only then can the students consciously and flexibly use the word guessing strategy in the reading process. Based on the students' different vocabulary level, the English teacher should provide opportunities for more learning.